৪৯তম বিসিএস ⎯ ফলিত রসায়ন [৫৪১]

• 'Amend' এর বাংলা পরিভাষা - সংশোধন করা।

অন্যদিকে,
• 'Amenable' অর্থ - সংবেদনশীল; চালিত বা নিয়ন্ত্রিত হতে আগ্রহী এমন; বাধ্য; অনুগত।
• 'Amends' অর্থ - ক্ষতিপূরণ দান করা।
• 'Augmenting' অর্থ - পরিবর্ধন করা।

উৎস: বাংলা একাডেমি, প্রশাসনিক পরিভাষা এবং অভিগম্য অভিধান।

• 'বাতাস' শব্দের সমার্থক শব্দ:
বায়ু, হাওয়া, পবন, সমীর, সমীরণ, অনিল, মরুৎ, প্রভঞ্জন।

অন্যদিকে,
• 'পানি' শব্দের সমার্থক শব্দ: অম্বু, জল, নীর, সলিল, অপ, উদক, তোয়, জীবন ইত্যাদি।
• 'তুষার' শব্দের সমার্থক শব্দ: বরফ; হিমানী; নীহার।
• 'মেঘ' শব্দের সমার্থক শব্দ: জলধর; জীমূত; বারিদ; নীরদ; পায়োদ; ঘন।

উৎস: বাংলা একাডেমি, আধুনিক বাংলা অভিধান; অভিগম্য অভিধান এবং ভাষা-শিক্ষা, ড. হায়াৎ মামুদ।

• ভারতচন্দ্র রায়:
- কবি রায়গুণাকর ভারতচন্দ্র আঠার শতকের শ্রেষ্ঠ কবি। তিনি মধ্যযুগের বাংলা সাহিত্যের অন্যতম শ্রেষ্ঠ কবি হিসেবেও মর্যাদার অধিকারী। মঙ্গলকাব্য ধারার শেষ কবি ভারতচন্দ্র বিদ্যাসুন্দর কাহিনিরও শ্রেষ্ঠ কবি রূপে পরিগণিত।

- কবি ভারতচন্দ্রের প্রতিভার শ্রেষ্ঠ নিদর্শন 'অন্নদামঙ্গল' কাব্য। 'কালিকামঙ্গল' ও 'বিদ্যাসুন্দর' এই কাব্যের অংশমাত্র।
- ভারতচন্দ্র ছিলেন 'ব্যাকরণ অভিধান সাহিত্য নাটক অলঙ্কার সঙ্গীত শাস্ত্রের অধ্যাপক এবং পুরাণ-আগম-পারসী-নাগরী -বেত্তা।'

- ভারতচন্দ্রের জন্মকাল নিয়ে মতানৈক্য আছে। ঈশ্বরগুপ্ত কর্তৃক উল্লেখিত ১৭১২ সাল সঠিক জন্মসাল নয়। বিভিন্ন তথ্য ও অনুমান মিলিয়ে সিদ্ধান্ত করা হয়েছে যে, ভারতচন্দ্র আঠার শতকের গোড়ার দিকে ১৭০৫ থেকে ১৭১০ সালের মধ্যে জন্মগ্রহণ করেছিলেন। ড. আশুতোষ ভট্টাচার্য সর্বশেষ তথ্য বিবেচনা করে ১৭০৭ সালে ভারতচন্দ্রের জন্ম হয়েছিল বলে মনে করেন। রায়গুণাকর ভারতচন্দ্র বর্তমান বর্ধমান বিভাগের ভুরসুট পরগনায় আধুনিক হাওড়া জেলার পেঁড়ো (পান্ডুয়া) গ্রামে জন্মগ্রহণ করেন।

- চল্লিশ বৎসর বয়সে ভারতচন্দ্র নবদ্বীপের রাজা কৃষ্ণচন্দ্র রায়ের সভাকবি নিযুক্ত হন। তাঁর মাসিক বেতন হয় চল্লিশ টাকা। কবি মহারাজ কৃষ্ণচন্দ্রকে প্রতিদিন কবিতা রচনা করে শোনাতেন। তাঁর কবিত্বে মুগ্ধ হয়ে রাজা তাঁকে 'গুণাকর' উপাধি প্রদান করেন এবং প্রচুর ভূসম্পত্তি উপহার দেন।

- ভারতচন্দ্র মহারাজ কৃষ্ণচন্দ্রের আদেশে 'অন্নদামঙ্গল' কাব্য রচনা করেন। কবি গ্রন্থোৎপত্তি সম্পর্কে বলেছেন যে, একদিকে দেবীর আদেশ, অন্যদিকে রাজার আদেশে কাব্য রচনা করেছেন।

অন্যদিকে,
• বিদ্যাপতি ছিলেন মিথিলার কবি। মিথিলার রাজসভার কবি বিদ্যাপতি মৈথিলি ভাষায় সুন্দর পদাবলি ও অন্যান্য গীতিকবিতা রচনা করে সকলকে মুগ্ধ করেছেন বলে তাঁকে 'মৈথিল কোকিল' বলা হয়। তিনি ছিলেন ব্রজবুলি বৈষ্ণব কবি এবং পদসঙ্গীত ধারার রূপকার। তাঁর শ্রেষ্ঠ কীর্তি হচ্ছে ব্রজবুলিতে রচিত রাধাকৃষ্ণ বিষয়ক পদ।

• চণ্ডীদাস চৈতন্যপূর্ব যুগের কবি ছিলেন। চণ্ডীদাসকে বাংলা ভাষার প্রথম মানবতাবাদী কবি বলা হয়।

• মুকুন্দরাম চক্রবর্তীর উপাধি ছিল কবিকঙ্কন।মধ্যযুগের বাংলা সাহিত্যে মানব রসের তিনি প্রথম এবং একমাত্র স্রষ্টা। মুকুন্দরাম চক্রবর্তীকে দুঃখ-বর্ননার কবি হিসাবেও আখ্যায়িত করা হয়।

উৎস: বাংলা সাহিত্যের ইতিহাস, ড. মাহাবুবুল আলম।

• লুইপা:
- 'চয্যাচর্যবিনিশ্চয়'-এর প্রথম কবি লুইপা। তিব্বতি ঐতিহ্যে প্রাপ্ত চুরাশি জন সিদ্ধাচার্যের নামের তালিকায় লুইয়ের নাম আদিতম। অনেক পণ্ডিত লুইপাকে প্রথম চর্যাগীতি রচয়িতা বলে মনে করেন। তাঁর জীবনকাল ৭৩০-৮১০ খ্রিষ্টাব্দের মধ্যে। সে সময় ছিল রাজা ধর্মপালের রাজত্বকাল। হিন্দিভাষীরা লুইপাকে মগধ বা বিহারের অধিবাসী বলে দাবি করেন।

- যোগতন্ত্রশাস্ত্রেও লুইপার উল্লেখ রয়েছে। তন্ত্রশাস্ত্রের লুইপার অন্য নাম মীননাথ বা মৎস্যেন্দ্রনাথ। মৎস্যের সঙ্গে নামের মিল থাকায় কোনো কোনো পণ্ডিত লুইকে শবরপা-এর শিষ্য ও ধীবর সম্প্রদায়ের অন্তর্ভুক্ত বলে উল্লেখ করেন। এ লুইপা আদি সিদ্ধাচার্য (সকল সিদ্ধাচার্যের গুরু) বলে অনেকের ধারণা।

- লুইপাকে সংস্কৃত টীকাকার মুনি দত্ত আদি সিদ্ধাচার্য বলে উল্লেখ করেছেন। তবে, তারানাথের মতে, লুইপা চতুর্থ সিদ্ধাচার্য, আর সরহ হলেন আদি সিদ্ধাচার্য। তাঁর মতে, লুইপা ছিলেন উড্ডীয়ান-রাজ উদয়নের কর্মচারী। তিনি শবর পা-র শিষ্যত্ব গ্রহণ করেছিলেন। চর্যাগীতির লুইপা আর তন্ত্রশাস্ত্রের লুইপা অভিন্ন নয় বলেই মনে করা হয়। কেননা বলা হয়েছে, লুইপা ছিলেন গৌড় অঞ্চলের অধিবাসী। আর তন্ত্রশাস্ত্রের মীননাথ বা মৎস্যেন্দ্রনাথের বাড়ি দক্ষিণবঙ্গে। তিনি ছিলেন গোরক্ষনাথের গুরু। তাই ধারণা করা হয়, লুইপা ও মীননাথ অভিন্ন ব্যক্তি নয়।

- হরপ্রসাদ শাস্ত্রীর ধারণা লুইপা ছিলেন বাঙালি। রাহুল সাংস্কৃত্যায়নের মতে, লুইপা রাজা ধর্মপালের সচিব হিসেবে দায়িত্ব পালন করেন।

- লুইপা বহু গ্রন্থ রচনা করেছেন। তিব্বতি অনুবাদের মাধ্যমে লুইয়ের বৌদ্ধ দর্শন বিষয়ক তিনটি গ্রন্থের নাম পাওয়া যায়। এগুলো হলো: 'শ্রীভগবদভিসময়', 'অভিসময়বিভঙ্গ' ও 'তত্ত্বস্বভাবদোহাকোষগীতিকাদৃষ্টিনাম'। প্রথম দুটি বই দর্শনের এবং তৃতীয়টি দোঁহা ও গানের।

উৎস: বাংলা সাহিত্যের ইতিহাস, ড. মাহাবুবুল আলম।

• মিছিল (বিশেষ্য পদ),
- এটি ফারসি ভাষার শব্দ।
অর্থ:
- শোভাযাত্রা (মহরমের মিছিল)।
- মোকদ্দমা ও তৎসম্বন্ধীয় নথিপত্র।
- বিন্যাস, সিজিল।
- সমান, সমকক্ষ।

• ফারসি ভাষা থেকে আগত কিছু শব্দ হলো:
গ্রেপ্তারি, গ্রেফতার, দারোগা, দারোয়ান, সাদা, খরগোশ, কাজি, খোয়াব, চেহারা, কাগজ, চশমা, চাকর, চারপায়, ছয়লাপ ইত্যাদি।

উৎস: বাংলা একাডেমি, আধুনিক বাংলা অভিধান।

• ধ্বনি:
- ভাষার ক্ষুদ্রতম একক ধ্বনি। কোনো ভাষার উচ্চারিত শব্দকে সূক্ষ্মভাবে বিশ্লেষণ করলে তার যে অবিভাজ্য ক্ষুদ্রতম অংশ পাওয়া যায়, তা-ই ধ্বনি। মানুষের বাগ্‌যন্ত্রের সহায়তায় উচ্চারিত ধ্বনি থেকেই ভাষার সৃষ্টি। বস্তুত ভাষাকে বিশ্লেষণ করলে চারটি মৌলিক উপাদান পাওয়া যায়। এই উপাদানগুলো হলো-ধ্বনি, শব্দ, বাক্য ও অর্থ।

- মানুষ তার মনের ভাব প্রকাশ করার জন্য 'কথা' বলে। মানুষের 'কথা' হলো অর্থযুক্ত কিছু ধ্বনি। ব্যাকরণ শাস্ত্রে মানুষের কণ্ঠনিঃসৃত শব্দ বা আওয়াজকেই ধ্বনি বলা হয়। বস্তুত অর্থবোধক ধ্বনিসমূহই মানুষের বিভিন্ন ভাষার বাধ্বনি। ধ্বনিই ভাষার মূল ভিত্তি।

- ধ্বনি নির্গত হয় মুখ দিয়ে। ধ্বনি উৎপাদনে মুখ, নাসিকা, কণ্ঠ প্রভৃতি বাক্-প্রত্যঙ্গ ব্যবহৃত হলেও ধ্বনি উৎপাদনের মূল উৎস হলো ফুসফুস। ফুসফুসের সাহায্যে আমরা শ্বাস গ্রহণ ও ত্যাগ করি। ফুসফুস থেকে বাতাস বেরিয়ে আসার সময় বিভিন্ন বাক্-প্রত্যঙ্গের সংস্পর্শে আসে। ফুসফুস থেকে বাতাস স্বরযন্ত্রের মধ্য দিয়ে বেরিয়ে আসার সময় মুখের বিভিন্ন জায়গায় ঘষা খায়। এই ঘর্ষণের ফলে মুখে নানা ধরনের ধ্বনির সৃষ্টি হয়।

- অর্থাৎ ফুসফুস নির্গত বাতাস স্বরযন্ত্রের মধ্য দিয়ে মুখগহ্বরে প্রবেশের পর বিভিন্ন বাক্-প্রত্যঙ্গের সংস্পর্শে আঘাত লাগার দরুন ধ্বনি গঠিত বা তৈরি হয়। ধ্বনি গঠনে বিভিন্ন বাক্- প্রত্যঙ্গের ভূমিকা অত্যন্ত গুরুত্বপূর্ণ।

উৎস: বাংলা ব্যাকরণ ও নির্মিতি, সপ্তম শ্রেণি।

• আনা (য়ানা) -আনি (য়ানি) বিদেশি তদ্ধিত প্রত্যয়: ভাব, অভ্যাস বা আচরণ অর্থে বিশেষ্য শব্দ গঠন করে।
যেমন:
ঘর + আনা = ঘরানা,
গরিব + আনা = গরিবানা,
বাবু + আনা = বাবুয়ানা,
বিবি + আনা = বিবিয়ানা ইত্যাদি।

আবার,
বাবু + আনি = বাবুআনি > বাবুয়ানি।

• এরূপ কিছু বিদেশি তদ্ধিত প্রত্যয় হলো-
-ওয়ান, -খানা, -খোর, -গর, -গিরি, -চা > চি, -চী > চি, -তর (তরো), -দান, -দানি, -সার, -নবিশ, -বন্দি, -বাজ /-বাজি, -সহি, সই, -স্তান।

উৎস: ভাষা-শিক্ষা, ড. হায়াৎ মামুদ।

• যুক্তবর্ণের অশুদ্ধ গঠন- ঞ্‌ + ক = ঙ্ক।
- শুদ্ধরূপ: ঙ্‌ + ক = ঙ্ক।

---------------
• যুক্তবর্ণ:
একাধিক বর্ণ যুক্ত হয়ে যুক্তবর্ণ তৈরি হয়। যুক্ত হওয়া বর্ণগুলোকে দেখে কখনো সহজে চেনা যায়, কখনো সহজে চেনা যায় না। এদিক দিয়ে যুক্তবর্ণ দুই রকম: স্বচ্ছ ও অস্বচ্ছ।

গুরুত্বপূর্ণ কিছু যুক্তবর্ণ হলো-
- জ্‌ + ঞ = জ্ঞ;
- ঞ্‌ + জ = ঞ্জ;
- ঞ্‌ + চ = ঞ্চ;
- ঞ্‌ + ছ = ঞ্ছ;
- ষ্‌ + ণ = ষ্ণ।

উৎস: ভাষা-শিক্ষা, ড. হায়াৎ মামুদ।

• বিশেষ্যের জায়গায় বিশেষণের কিংবা বিশেষণের বাহুল্য প্রয়োগজনিত ভুল:
বাক্যের মধ্যে ব্যবহৃত বিশেষ্য পদকে বিশেষণ কিংবা বিশেষণ পদকে বিশেষ্য ভেবে পদ পরিবর্তন করলে এ ধরনের ভুল হয়।
যেমন- আবশ্যক শব্দটি বিশেষণ হিসেবে ব্যবহৃত হয়। এর বদলে ঈয় প্রত্যয় যোগ করে আবশ্যকীয় শব্দের ব্যবহার যথাযথ নয়।
যেমন
অশুদ্ধ: অনাবশ্যকীয় ব্যাপারে কৌতূহল ভালো নয়।
শুদ্ধ: অনাবশ্যক ব্যাপারে কৌতূহল ভালো নয়।

অশুদ্ধ: ইহার আবশ্যক নাই।
শুদ্ধ: হার আবশ্যকতা নাই।

অশুদ্ধ: রাঙ্গামাটি পার্বতীয় এলাকা।
শুদ্ধ: রাঙ্গামাটি পার্বত্য এলাকা।

অশুদ্ধ: বাংলাদেশ একটি উন্নতশীল দেশ।
শুদ্ধ: বাংলাদেশ একটি উন্নয়নশীল দেশ।

উৎস: ভাষা-শিক্ষা, ড. হায়াৎ মামুদ।

• বিশেষণ পদ নয়- সততা।
- 'সততা' গুণবাচক বিশেষ্য পদ।

• আদ্য প্রত্যয় বা উপসর্গযুক্ত বিশেষণ: এ ধরনের বিশেষণ আদ্যপ্রত্যয় বা উপসর্গযোগে গঠিত হয়।
যেমন:
- নিখুঁত (নি + খুঁত) কাজ।
- সুকঠিন (সু + কঠিন) প্রতিজ্ঞা।
- দুঃসহ (দুঃ + সহ) দারিদ্র্য।

উৎস: ভাষা-শিক্ষা, ড. হায়াৎ মামুদ এবং বাংলা একাডেমি, আধুনিক বাংলা অভিধান।

• শুদ্ধ বানান: গৃহস্থ।
- এটি বিশেষ্য পদ।
- সংস্কৃত ভাষার শব্দ।
অর্থ:
- সংসার ধর্ম পালন করে এমন,
- গৃহী।

অন্যদিকে,
• প্রশস্ত, অভ্যস্ত ও ব্যস্ত বানানগুলো শুদ্ধ।

• এরূপ কিছু শুদ্ধ শব্দ- ঠোঁটস্থ, মুখস্থ, দ্বারস্থ, অস্ত, কণ্ঠস্থ, গ্রস্ত।

উৎস: বাংলা একাডেমি, আধুনিক বাংলা অভিধান।

• 'কালো বরফ' উপন্যাস:
- ১৯৭৭ সালের ২১-৩০ আগস্ট মাহমুদুল হক রচনা করেন 'কালো বরফ' উপন্যাসটি, কিন্তু এর প্রকাশকাল অনেক পরে ১৯৯২ সালে।
- এটি ছেচল্লিশের দাঙ্গা ও ১৯৪৭ সালের দেশভাগকে কেন্দ্র করে রচিত।
- উপন্যাসটিতে হিন্দু-মুসলমানের বিরোধ-দাঙ্গা, দ্বেষ-ক্ষোভ এবং মিলন-বিরহ পরিস্ফুটিত হয়েছে।
- উপন্যাসের প্রধান চরিত্র- আব্দুল খালেক।

অন্যদিকে,
-----------------
• 'খেলাঘর' (১৯৮৮): এটি মুক্তিযুদ্ধভিত্তিক উপন্যাস। চরিত্র: রেহানা, মুকল ও ইয়াকুব। ২০০৬ সালে উপন্যাসটির চলচ্চিত্রায়ন করা হয়।

• 'একটি কালো মেয়ের কথা' উপন্যাস: বাংলাদেশের স্বাধীনতা সংগ্রাম নিয়ে রচিত তারাশঙ্কর বন্দ্যোপাধ্যায়ের উপন্যাস- 'একটি কালো মেয়ের কথা'। এটি প্রকাশিত হয় ১৯৭১ খ্রিষ্টব্দে। এটি তাঁর সর্বশেষ উপন্যাস।

• "কালো ঘোড়া" লেখক ইমদাদুল হক মিলন রচিত একটি উপন্যাস। ১৯৮১ সালে পশ্চিম জার্মানির সিনডেল ফিঙেন শহরে বসে তিনি এই উপন্যাসটি রচনা করেন এবং এটি বাংলাদেশের একটি নিবিড় গ্রামকে কেন্দ্র করে আবর্তিত হয়। ‘কালোঘোড়া’ মুক্তিযুদ্ধের উপন্যাস। ১৯৭১ এর সেই জেগে ওঠার দিনে বাংলাদেশের একটি গ্রামে কেমন চেহারা নিয়েছিল মুক্তিযুদ্ধ, কেমন করে মুক্তিযুদ্ধ প্রভাবিত করেছিল গ্রামের প্রতিটি মানুষকে, কেমন করে মুক্তিযোদ্ধারা এসে আশ্রয় পায় এক বালকের কাছে, কেমন করে প্রাণ হারায় এব বোবা যুবতী, স্বাধীনতা বিরোধী চক্রের হোতা কেমন করে নিহত হয় মুক্তেোদ্ধাদের হাতে আর কেমন করেই বা মুক্তিযোদ্ধাদের আশ্রয়দাতা সেই বালক নিজের অজান্তে হয়ে ওঠে এক মহান মুক্তিযোদ্ধা, প্রাণের বিনিময়ে যে রক্ষা করতে চায় সহযোদ্ধাদের কে, এরকম অনেকগুলো বিষয়কে ‘কালোঘোড়া’ উপন্যাসে উপজীব্য করেছেন ইমদাদুল হক মিলন।

উৎস: 'কালো বরফ' ও "কালো ঘোড়া" উপন্যাস; বাংলা ভাষা ও সাহিত্য জিজ্ঞাসা এবং বাংলাপিডিয়া।

• 'বিসর্জন' নাটক:
- 'বিসর্জন' রবীন্দ্রনাথ ঠাকুর রচিত একটি নাটক। 'রাজর্ষি' উপন্যাসের প্রথমাংশ অবলম্বনে 'বিসর্জন' নাটকটি রচিত হয়।

- 'বিসর্জন' রবীন্দ্রনাথ ঠাকুরের মঞ্চসফল এবং জনপ্রিয় নাটকগুলির অন্যতম। রবীন্দ্রনাথ ঠাকুর স্বয়ং এই নাটকের প্রধান দুটি চরিত্র রঘুপতি ও জয়সিংহের ভূমিকায় বিভিন্ন সময়ে অভিনয় করেন।

- উদার ধর্মবোধ এবং সংকীর্ণ ধর্মীয় বিশ্বাসের মধ্যে দ্বন্দ্ব যেমন এই নাটকের প্রধান উপকরণ, তেমনই বিশ্বাসের উগ্রতা এবং মানব সম্পর্কের নিবিড়তা এই নাটকের প্রধান বৈশিষ্ট্য।
- রবীন্দ্রনাথ রচিত বিসর্জন নাটকে গোমতী নদীর কথা উল্লেখ আছে। নাটকটি অমিত্রাক্ষর ছন্দে রচিত।

উল্লেখযোগ্য চরিত্র:
- রঘুপতি,
- জয়সিংহ,
- অপর্ণা,
- গুণবতী,
- গোবিন্দমাণিক্য।

অন্যদিকে,
• 'ডাকঘর' নাটকের উল্লেখযোগ্য চরিত্র: অমল, সুধা, ঠাকুর্দা প্রমুখ।
• 'মুক্তধারা' নাটকের উল্লেখযোগ্য চরিত্র: অভিজিৎ, রণজিত, সুমন, অম্বা, বিভূতি।
• "প্রায়শ্চিত্ত" নাটকের চরিত্রগুলো: ধনঞ্জয়, সুরমা, উদয়াদিত্য, বিভা ইত্যাদি।

-------------------
তাঁর রচিত উল্লেখযোগ্য নাটক:
- রুদ্র চন্দ্র,
- বাল্মিকী প্রতিভা,
- কালের যাত্রা,
- তাসের দেশ,
- ডাকঘর,
- মালিনী ইত্যাদি।

উৎস: বাংলা ভাষা ও সাহিত্য জিজ্ঞাসা এবং বাংলাপিডিয়া।

• ফিলিস্তিনকে স্বীকৃতি:
- ২১ সেপ্টেম্বর, ২০২৫ যুক্তরাজ্য, কানাডা, অস্ট্রেলিয়া ও পর্তুগাল ফিলিস্তিনকে স্বীকৃতি দিয়েছে।
- বিশ্বের ধনী দেশগুলোর জোট জি-৭-এর সদস্যদের মধ্যে প্রথম ফিলিস্তিনকে স্বীকৃতি দিল যুক্তরাজ্য ও কানাডা।
- এর পর দিন ২২ সেপ্টেম্বর, ২০২৫ জাতিসংঘের সদর দপ্তর এক অনুষ্ঠানে ফিলিস্তিনকে আনুষ্ঠানিকভাবে রাষ্ট্র হিসেবে স্বীকৃতি দিয়েছে জাতিসংঘের নিরাপত্তা পরিষদের স্থায়ী সদস্য দেশ ফ্রান্স।
- এ নিয়ে জাতিসংঘের ১৯৩ সদস্যদেশের দেড় শ’র বেশি দেশ ফিলিস্তিনকে রাষ্ট্র হিসেবে স্বীকৃতি দিয়েছে।
- এর মধ্যে এশিয়া, আফ্রিকা, লাতিন ও মধ্য আমেরিকার দেশই বেশি।
- ১৯৮৮ সালের ১৬ নভেম্বর ফিলিস্তিনকে স্বীকৃতি দেয় বাংলাদেশ।
- জাতিসংঘের নিরাপত্তা পরিষদের স্থায়ী পাঁচ সদস্যের মধ্যে ফিলিস্তিন রাষ্ট্রকে এ পর্যন্ত শুধু যুক্তরাষ্ট্র স্বীকৃতি দেয়নি।

সূত্র- প্রথম আলো পত্রিকা প্রতিবেদন।

• ফেডারেল সিভিল সার্ভিস কমিশন:
- মার্কিন যুক্তরাষ্ট্রে সংবিধিবদ্ধভাবে ফেডারেল সিভিল সার্ভিস কমিশন গঠিত হয় ১৮৮৩ সালে।
- The Pendleton Civil Service Reform Act-1883 এর মাধ্যমে।
- ১৯৭৮ সালে ফেডারেল সিভিল সার্ভিস কমিশনে সংস্কার করে একে তিনটি প্রতিষ্ঠানে বিকেন্দ্রীকরণ করা হয়। এগুলো হলো:
- অফিস অব দ্য পার্সোনেল ম্যানেজমেন্ট
- দ্য মেরিট সিস্টেম প্রোটেকশন বোর্ড
- দ্য ফেডারেল লেবার রিলেশন অথরিটি।

উৎস: অফিস অব দ্য পার্সোনেল ম্যানেজমেন্ট ওয়েবসাইট।

• জাপাদ-২০২৫:
- জাপাদ-২০২৫ হলো রাশিয়া ও বেলারুশের যৌথ সামরিক মহড়া।
- এই মহড়া ১২ সেপ্টেম্বর, ২০২৫ শুরু হয় এবং ১৭ সেপ্টেম্বর, ২০২৫ শেষ হয়।
- এই মহড়ায় প্রায় ১ লাখ সেনা অংশগ্রহণ করে, যার মধ্যে ভারী অস্ত্র, বোমারু বিমান, যুদ্ধজাহাজ এবং প্যারাট্রুপারদের সমন্বয়ে ব্যাপক সামরিক কৌশল প্রদর্শন করা হয়।
- যুক্তরাষ্ট্রসহ ২৩টি দেশের প্রতিনিধিরা মহড়া দেখতে বেলারুশে উপস্থিত ছিলেন।
- মহড়ার মূল উদ্দেশ্য ছিল সীমান্তবর্তী অঞ্চলে সম্ভাব্য আগ্রাসন প্রতিহত করার জন্য প্রস্তুতি প্রদর্শন।

তথ্যসূত্র- প্রথম আলো পত্রিকা প্রতিবেদন।

Continuous processes require precise and reliable control of:
1.Temperature, pressure, flow rates, and composition over long operating periods.
Microprocessors and advanced process control systems (DCS/PLC):
1.Allow real-time monitoring and feedback control.
2.Enable safe and efficient operation of continuous reactors, distillation columns, and chemical plants.

Other options:
(ক) Catalysts → accelerate reactions but do not inherently enable continuous operation.
(গ) Bunsen burner → laboratory heating device, irrelevant for industrial scale.
(ঘ) Vacuum pumps → assist specific processes (distillation, drying) but don’t enable continuous control.

Mid-20th century polymerization technologies (e.g., addition and condensation polymerization) enabled large-scale production of:
1.Plastics: polyethylene, polypropylene, polystyrene, PVC
2.Synthetic fibers: nylon, polyester
Industrial need addressed:
1.Lightweight alternatives to metals and wood
2.Durable, corrosion-resistant materials for packaging, construction, automotive, and consumer goods

Other options:
(ক) High-strength metals → unrelated to polymerization
(খ) Production of natural fibers → natural fibers existed already (cotton, wool)
(গ) Reducing crude oil dependency → polymers are derived from petroleum, so initially increased dependency

1.Unit operations are physical processes (e.g., separation, heat transfer) that do not change chemical composition.
2.Unit processes are chemical transformations that produce a chemical change (e.g., oxidation, hydrogenation).
3.Crystallization of salt from brine can be:
Unit operation → when viewed as a physical separation of solid NaCl from water.
Unit process → when impurities react or the crystallization involves chemical changes (e.g., controlled formation of specific hydrates or co-crystals).

Other options:
(ক) Hydrogenation → strictly a unit process (chemical reaction).
(গ) Drying → unit operation (physical removal of moisture).
(ঘ) Filtration → unit operation (physical separation).

1.Integrated chemical process plants combine multiple related chemical processes within a single facility.
2.Primary environmental advantage:
Efficient utilization of raw materials → by-products of one process can be feedstocks for another.
Energy efficiency → heat integration and reduced energy losses.
Reduced emissions and waste → less effluent, solid waste, and gas discharge.

Other options:
(ক) Increased employment → may or may not happen; not an environmental advantage.
(খ) Reduced need for automation → false; integration often increases control complexity.
(ঘ) Elimination of catalysts → catalysts are still used; integration does not remove them.

1.After World War II, the rapid expansion of petrochemical industries was driven by:
Catalytic cracking of petroleum fractions → produces light olefins (ethylene, propylene) for further chemical synthesis.
Polymerization processes → convert olefins into plastics (polyethylene, polypropylene, PVC).
2.These technologies enabled mass production of synthetic polymers, solvents, and industrial chemicals from petroleum.

Other options:
(খ) Biomass feedstock → minor role; petrochemicals primarily used crude oil and natural gas.
(গ) Electrochemical cells → not a major driver for large-scale petrochemicals.
(ঘ) Large-scale electrolysis → used for metals and chlorine, not general petrochemical production.

1.Unit operation:
Refers to physical transformations of materials without changing chemical composition.
Examples: distillation, filtration, evaporation, drying, crystallization.
2.Unit process:
Refers to chemical transformations, where new substances are formed.
Examples: oxidation, hydrogenation, nitration, polymerization, saponification.

1.Unit operation: involves physical changes without altering chemical composition:
Distillation separates components based on differences in boiling points → purely physical process.
2.Unit process: involves chemical changes where new substances are formed.

Other options:
(ক) Nitration of benzene → chemical reaction → unit process
(খ) Ammonia synthesis → chemical reaction → unit process
(ঘ) Alkylation → chemical reaction → unit process

1.Unit process involves a chemical transformation of materials.
2.Hydrogenation of vegetable oils:
Unsaturated fatty acids (double bonds) are chemically converted to saturated fatty acids using hydrogen and a catalyst.
This changes the chemical composition of the oil → classic example of a unit process.

Other options:
(ক) Unit operation → physical changes only (e.g., distillation, filtration).
(খ) Hybrid unit → combination of unit operation + process (less common term).
(ঘ) Utility process → supporting operations like steam generation, cooling water, electricity.

Unit operations involve physical changes without altering chemical composition:
Filtration → separates solids from liquids
Absorption → transfers a component from gas to liquid
Drying → removes moisture from solids or liquids
Unit processes involve chemical reactions, where new substances are formed:
Polymerization → monomers chemically react to form polymers → chemical change → unit process

1.Heat exchangers are designed to transfer thermal energy from a hot stream to a cold stream without mixing them.
2.Key points:
No chemical reaction occurs → purely physical energy transfer.
Common types: shell-and-tube, plate, finned-tube heat exchangers.

Other options:
(খ) Chemical transformation → unit process, not heat exchanger function
(গ) Separation by volatility → distillation or evaporation
(ঘ) Catalytic reaction → occurs in reactors, not heat exchangers

1.Circular economy aims to minimize waste and make the most of resources by keeping materials in use for as long as possible.
2.In chemical technology, this involves:
Designing processes that allow recycling of raw materials and by-products.
Recovering energy from waste streams.
Reducing environmental impact and reliance on virgin chemicals.

Other options:
(ক) Producing more virgin chemicals → opposite of circular economy principles.
(গ) Avoiding energy recovery → inefficient and unsustainable.
(ঘ) Relying on landfills → linear, not circular, approach.

1. Pre-conditions for setting up a chemical plant include:
Availability of raw materials → ensures continuous production.
Adequate market demand → ensures the products can be sold profitably.
Skilled workforce → needed for operation, maintenance, and safety.

2. Number of competitors is not a pre-condition; it is a market consideration but does not prevent plant setup.

1.Bulk chemical plants are water- and energy-intensive.
2.Critical infrastructure requirements include:
Reliable cooling water → for heat exchangers, condensers, and process cooling.
Effluent disposal or treatment system → to handle liquid waste and comply with environmental regulations.

Other options:
(ক) High-speed internet → useful but not critical for chemical reactions.
(খ) Proximity to residential areas → often avoided due to safety concerns.
(ঘ) Luxury housing → irrelevant to plant operation.

1.Financial pre-conditions ensure the chemical plant is economically viable:
Working capital → sufficient funds to cover raw materials, labor, and operational expenses.
Feasibility of payback period → ensures the investment can be recovered in a reasonable time.

Other options:
(খ) Low raw material cost → helpful but not sufficient alone.
(গ) High price volatility → risky, not a pre-condition.
(ঘ) Ignoring ROI → would make the project financially unsustainable.

1.Multi-criteria decision matrix is used to evaluate potential sites based on several important factors.
2.Key factors typically include:
Raw material availability → ensures continuous supply.
Logistics → proximity to markets and transportation facilities.
Safety → risk of hazards and accidents.
Environmental compliance → ability to meet regulations.

Other options:
(খ) Location glamour, climate, entertainment → irrelevant for industrial viability.
(গ) Land cost and tax benefits only → important but not the full picture.
(ঘ) Political factors only → part of the evaluation, but insufficient alone.

Newtonian fluids:
1.Viscosity is independent of shear rate.
2.Examples: water, air, ethanol.
3.Flow behavior is linear: shear stress ∝ shear rate.
Non-Newtonian fluids:
1.Viscosity changes with shear rate or stress.
2.Examples: ketchup (shear-thinning), cornstarch suspension (shear-thickening), toothpaste (has yield stress).

Other options:
(খ) Viscosity typically decreases with temperature for most Newtonian fluids, not increases.
(গ) Yield stress → characteristic of some non-Newtonian fluids, not Newtonian fluids.
(ঘ) Viscosity comparison → depends on specific fluids; not a defining feature.

Euler’s equation describes the motion of a perfect (inviscid) fluid.
Assumptions for Euler’s equation:
1.Inviscid fluid → neglects viscous effects.
2.Non-conducting / adiabatic → no heat transfer; entropy remains constant along a streamline.
3.Can be applied to compressible or incompressible flows.

Other options:
(ক) Turbulent flow → Euler’s equation assumes ideal laminar flow, though it can be applied in an average sense.
(খ) Negligible external body forces → body forces (like gravity) can be included in Euler’s equation.
(গ) Non-accelerating → Euler’s equation applies to accelerating flows as well.

Venturi meter:
A flow measurement device that uses a gradual converging-diverging section to measure flow rate via pressure difference.
Advantages over an orifice meter:
Lower permanent pressure drop → due to smooth flow transition.
Higher accuracy → less energy loss and less turbulence.
Orifice meter:
Sharp-edged constriction → higher pressure drop and more energy loss.
Accuracy is lower compared to a Venturi meter.

Bernoulli’s equation assumes:
1.Inviscid (non-viscous) fluid → no energy loss due to friction.
2.Steady flow → velocity at each point does not change with time.
3.Along a streamline → applies only along a single streamline.
4.Incompressible or slowly varying density → usually incompressible, but can be extended for compressible flows under certain assumptions.

Other options:
(ক) Not valid for real viscous fluids without correction (friction losses must be considered).
(খ) Friction and turbulence losses are not included in the basic Bernoulli equation.
(গ) Can be applied to compressible flows under certain approximations (low Mach number, isentropic flow).

Simple piezometer:
1.Measures the static pressure of a fluid in a pipe.
2.Not influenced by fluid velocity → only responds to the pressure head.
3.Typically a vertical tube connected to the pipeline; the height of the liquid column indicates pressure.

Other options:
(ক) Pitot-static tube → measures both static and dynamic pressure; dynamic pressure depends on velocity.
(গ) Venturi meter → measures flow rate using pressure difference, influenced by velocity.
(ঘ) Rotameter → measures flow rate, indirectly related to velocity, not just static pressure.

1.Anodic protection is a corrosion control technique where a metal is made the anode and its potential is controlled to reduce corrosion.
2.Principle:
The metal is maintained in the passive region of its polarization curve, where:
A thin, stable oxide film forms on the surface.
Corrosion rate is drastically reduced.

Other regions:
Active region → metal corrodes rapidly.
Transpassive region → metal starts dissolving again at very high potentials.
Immune region → metal is naturally resistant, not typically achieved via anodic protection.

1.Aluminum has a highly negative standard electrode potential, so thermodynamically it should corrode easily.
2.However, it exhibits excellent corrosion resistance because:
It rapidly forms a thin, dense, and adherent Al₂O₃ (alumina) layer on its surface.
This passive layer prevents further reaction with the environment.
The layer is self-healing if scratched in air or water.

Other options:
(খ) Thick oxide scale → not typical for normal aluminum corrosion resistance.
(গ) Continuous dissolution/reprecipitation → occurs in some metals but not the main reason for aluminum’s passivity.
(ঘ) Cathodic protection → not the reason; aluminum resists corrosion naturally.

Galvanic corrosion occurs when two dissimilar metals are electrically connected in an electrolyte:
1.Steel (anode) corrodes faster.
2.Copper (cathode) is protected.
Ways to minimize steel corrosion:
1.Coating the anodic metal (steel) → prevents electrolyte contact, stopping corrosion.
2.Decreasing cathode-to-anode area ratio → reduces galvanic current, but often less practical.

Other options:
(ক) Increasing cathode-to-anode area → increases galvanic corrosion, worse for steel.
(গ) Coating copper → protects copper but does not stop steel corrosion effectively if steel is exposed.
(ঘ) Adding chloride ions → accelerates corrosion, especially in seawater.

Electrochemical Impedance Spectroscopy (EIS):
1. A non-destructive electrochemical technique.
2. Measures the impedance of a metal/electrolyte interface over a range of frequencies.
Provides insights into:
1.Charge transfer resistance (R_ct) → related to corrosion rate.
2.Double-layer capacitance (C_dl) → indicates surface properties and film formation.

Other options:
(খ) Critical pitting potential → measured by potentiodynamic polarization, not EIS.
(গ) Stress corrosion susceptibility → requires mechanical testing combined with electrochemistry.
(ঘ) Pourbaix diagrams → theoretical thermodynamic maps, not obtained from EIS.

High-temperature environments (like gas turbines, boilers, and engines) are prone to:
1.Hot corrosion caused by deposition of molten salts (sulfates, chlorides) on metal surfaces.
2.These salts accelerate oxidation and degrade protective oxide layers.

Other options:
(ক) Stress corrosion cracking → occurs mainly in tensile-stressed components exposed to specific corrosive media, usually at moderate temperatures.
(খ) Crevice corrosion → occurs in narrow gaps with stagnant electrolyte, generally at lower temperatures.
(ঘ) Erosion corrosion → caused by fluid flow combined with corrosion, not primarily temperature-dependent.

In the iron–carbon phase diagram:
A₁ (eutectoid) temperature ~727 °C
At this temperature, austenite (γ-Fe) with 0.8 wt% C transforms into pearlite, a lamellar mixture of ferrite (α) and cementite (Fe₃C).

Other points:
A₃ → temperature where ferrite starts forming from austenite in hypoeutectoid steels.
A₀ → not standard; sometimes used for lower transformations.
Acm → temperature where austenite with cementite transforms in hyper-eutectoid steels.

In basic oxygen furnace (BOF) steelmaking, sulfur removal (desulfurization) is limited by:
High oxygen potential in molten steel → sulfur tends to stay in solution because oxygen promotes the formation of SO₂ and reduces sulfur partitioning into slag.

Other factors:
(ক) Low basicity of slag → does reduce sulfur removal, but oxygen potential is the primary limiting factor.
(গ) Low temperature → slows reactions but not the main limitation in BOF.
(ঘ) High manganese → can slightly affect sulfur distribution, but oxygen activity dominates.

1.Pig iron contains higher silicon (~1–3%) because it is directly produced from the blast furnace.
2.During refining to wrought iron or steel (e.g., puddling or Bessemer process):
Silicon is strongly oxidized by oxygen in the slag.
Forms silica (SiO₂) which enters the slag, reducing Si content in the final iron.

Other options:
(খ) Silicon does not vaporize significantly at these temperatures.
(গ) Formation of SiC is not typical in conventional iron refining.
(ঘ) Silicon can dissolve in iron lattice, but oxidation removes it before this becomes significant.

1.Cast iron contains 2–4% carbon, which exceeds the solubility limit in iron.
2.Excess carbon forms:
Graphite flakes (in gray cast iron) → act as stress concentrators, making it brittle.
Cementite network (Fe₃C) (in white cast iron) → hard and brittle.
3.In contrast, steel has lower carbon content (~0.02–2%) → mostly forms ferrite and pearlite, giving ductility and toughness.

Other options:
(ক) Pearlite → tough, found in steel, not the main source of brittleness in cast iron.
(খ) Martensite → very hard, formed in quenched steel, not typical in as-cast cast iron.
(গ) Austenite → ductile at high temperatures, not responsible for brittleness.

1.In the LD (Linz–Donawitz) process, molten pig iron is refined to steel by blowing high-purity oxygen into the converter.
2.Supersonic oxygen jets serve to:
Ensure vigorous stirring of molten metal.
Promote rapid oxidation of impurities such as carbon, silicon, manganese, and phosphorus.
Enhance reaction kinetics and efficient heat distribution.

Other options:
(ক) Slag basicity → controlled by adding fluxes, not oxygen speed.
(খ) Nitrogen absorption → minimized by avoiding air, but not the reason for supersonic speed.
(ঘ) Erosion of refractory → too fast oxygen can actually increase wear; speed is optimized for mixing, not lining protection.

Murphree tray efficiency (E_M):
Measures how effectively a single tray approaches equilibrium.
Defined as:
EM=Actual change in composition on the tray/Change if the tray were at equilibrium

1.A theoretical plate assumes 100% equilibrium between vapor and liquid.
2.Real trays rarely achieve full equilibrium → Murphree efficiency accounts for this deviation.

Other options:
(খ) Reflux ratio → separate concept in distillation design.
(গ) Slope of operating line → McCabe–Thiele graphical method parameter.
(ঘ) Actual vs minimum stages → overall column efficiency, not tray-specific.

1.Reflux ratio (R): the ratio of liquid returned to the column to the distillate withdrawn.
2.Effect on the number of stages:
Minimum reflux ratio (R_min) → requires maximum number of theoretical stages.
Increasing R above R_min → more liquid returned, better contact between vapor and liquid, and fewer stages are needed to achieve the same separation.

Other options:
(ক) Decreasing reflux → increases number of stages, opposite effect.
(গ) Feed as saturated vapor → affects q-line slope, may reduce stages slightly but not as significantly as reflux increase.
(ঘ) Subcooled liquid feed → increases stages because the feed requires more vaporization.

1.Enthalpy–concentration method is used for distillation column design, especially when heat effects are significant.
2.In the stripping section:
The operating line relates the liquid and vapor compositions.
It is derived from the energy (enthalpy) balance around the reboiler, which provides the slope and intercept of the line in H–x or H–y space.

Other options:
(খ) Equilibrium relation → gives the equilibrium curve, not the operating line.
(গ) Mass balance around the feed tray → used for feed location determination, not stripping line slope.
(ঘ) Murphree efficiency → affects tray efficiency, not the operating line itself.

1.Uniform vapor distribution is critical for effective vapor–liquid contact on each tray.
2.Bubble-cap or sieve tray openings:
Allow vapor to pass through the liquid layer on the tray.
Promote even bubbling and mixing, preventing channeling or bypassing of liquid.

Other options:
(ক) Proper downcomer sizing → ensures liquid flow off the tray, not vapor distribution.
(গ) Adequate tray spacing → prevents flooding and provides mechanical clearance.
(ঘ) Column diameter → affects overall capacity but not vapor uniformity on a tray.

1.Reflux ratio = (liquid returned to column) / (distillate withdrawn).
2.At constant number of stages, increasing the reflux ratio means more liquid is recycled, improving rectification in the enriching section.
3.This increases top (distillate) purity, because the rising vapor is repeatedly contacted with more liquid.
4.At the same time, the bottom product also becomes purer, because less of the more volatile component escapes downward.

1.COP of absorption refrigeration = (Cooling effect) ÷ (Heat input to generator).
2.In a multi-effect absorption system, improving COP means reducing external heat input demand without reducing cooling capacity.

Other options:
(ক) Increasing generator temperature in all effects simultaneously → raises driving potential, but also increases heat input requirement; does not necessarily maximize COP.
(গ) Decreasing condenser temperature only → helps performance, but mainly affects capacity rather than fundamental COP improvement
(ঘ) Reducing evaporator temperature in last effect → lowers cooling effect → reduces COP.

1.In an ammonia–water absorption refrigeration cycle, the absorber’s job is to absorb ammonia vapor into water coming from the generator, forming strong solution.
2.The solubility of ammonia in water increases when pressure is low and temperature is low.
3.That’s why the absorber is kept at low pressure → it enhances the driving force for absorption of ammonia vapor into water.
Now check the options:

Other options:
খ) Increase generator temperature -unrelated; generator is separate.
গ) Reduce condenser cooling load - that’s condenser duty, not absorber pressure.
ঘ) Improve vaporization in evaporator evaporator-already runs at low pressure, not the absorber.

Exergy loss = irreversibility in a component.
Evaporator: some exergy loss due to finite ΔT heat transfer, but relatively small.
Condenser: heat rejection to surroundings at finite ΔT, but not the dominant irreversibility.
Expansion valve (throttling): this is an isenthalpic process, highly irreversible because pressure drops without work recovery → major source of exergy destruction.
Compressor: adiabatic compression has some irreversibility (friction, non-idealities), but usually less than throttling losses.

1.Halocarbon refrigerants (CFCs, HCFCs, HFCs):
1.Generally non-toxic and non-flammable, so option খ is wrong.
2.Some have low critical temperatures, but most are used in moderate-temperature systems; not the major limitation.
3. Latent heat of vaporization is usually lower than ammonia, but this mainly affects system size, not a fundamental limitation.
4. Major concern: environmental impact — ozone depletion (for CFCs/HCFCs) and high global warming potential (GWP).
2.Ammonia (R-717): very efficient, zero ODP, negligible GWP, but toxic and slightly flammable.

1. In an ammonia–water absorption system, after the generator, the vapor leaving contains some water along with ammonia.
2. If water reaches the condenser, it can freeze (especially in low-temperature systems) or reduce refrigeration efficiency.
3. The rectifier is a small column above the generator that separates water from ammonia vapor, allowing mostly pure ammonia vapor to go to the condenser.

1.Limestone = mainly calcium carbonate (CaCO₃).
2.Acid rain contains sulfuric and nitric acids, which react with CaCO₃.
3.Reaction with sulfuric/nitric acid:
CaCO₃+H₂SO₄→CaSO₄+CO₂+H₂O
or in case of weak acid (carbonic acid in rain):
CaCO₃+H⁺→Ca²⁺ (soluble)+HCO₃⁻
4.This dissolves the limestone, leading to erosion.

1.BOD (Biochemical Oxygen Demand) measures the amount of dissolved oxygen required by microorganisms to decompose organic matter in water over a specified period (usually 5 days at 20 °C).

2.Therefore, it directly reflects the level of organic pollution in wastewater.

1.The Kyoto Protocol introduced flexible mechanisms to help countries meet their emission targets cost-effectively:
Emission Trading – countries can trade surplus emission allowances.
Clean Development Mechanism (CDM) – investing in emission reduction projects in developing countries to earn credits.
Joint Implementation (JI) – industrialized countries invest in emission reduction projects in other industrialized countries for credits.
2.Other options like national bans, CO₂ taxation, or CFC phase-out are not part of Kyoto’s flexible mechanisms.

1.The Montreal Protocol (1987) is an international treaty aimed at protecting the ozone layer.
2.It mandates the gradual phase-out of ozone-depleting substances (ODS), including CFCs, halons, and HCFCs.
3.It does not regulate CO₂, NO₂, or SO₂.
4.It is legally binding for all parties, with different timelines for developed and developing countries.

1.Incineration with energy recovery:
Burns hazardous waste → reduces volume drastically.
Converts much of the waste into inert ash.
Generates energy (electricity or heat).
Requires proper flue gas treatment to control pollutants like dioxins, furans, and heavy metals.
2.Landfilling: risk of leachate contamination and long-term monitoring.

1.Alum (Al₂(SO₄)₃·18H₂O) is used as a coagulant in water treatment to remove suspended solids.
2.The optimum dose depends on:
pH (affects hydrolysis and floc formation)
Alkalinity (buffers pH changes caused by alum addition)
Turbidity (amount of suspended solids to be removed)
3.Other factors like dissolved oxygen, temperature, or chloride concentration are less critical in determining the alum dose.

Ultrafiltration (UF):
1.Membrane pore size ~0.01–0.1 µm
2.Removes colloids, suspended solids, bacteria, and macromolecules
3.Does not remove most dissolved salts

Reverse Osmosis (RO):
1.Very fine, semi-permeable membrane
2.Requires high pressure to overcome osmotic pressure
3.Removes almost all dissolved salts, organics, and microorganisms

1.High-pressure boilers are very sensitive to water impurities.
2.Priming and foaming are mainly caused by hardness ions (Ca²⁺, Mg²⁺) forming insoluble salts that carry over with steam.
3.Corrosion can be aggravated by dissolved salts (chlorides, sulfates), but hardness is the primary concern for high-pressure boilers.
4.Dissolved gases like N₂ are less critical compared to O₂ and CO₂ for corrosion.

The adsorption capacity of activated carbon depends primarily on:
Contact time – More time allows more pollutant molecules to diffuse into the pores of the carbon.
Temperature – Adsorption is usually exothermic; higher temperatures can reduce capacity.
Initial concentration of pollutants – Higher concentrations increase the driving force for mass transfer onto the carbon surface.
Other factors like chlorine, turbidity, or pH in the typical range of 6–8 have much smaller effects compared to the above.

BOD/COD ratio = 600 / 1200 = 0.5
Interpretation:
0.6 → highly biodegradable, normal biological treatment works well
0.3–0.6 → moderately biodegradable, may require longer retention times or enhanced biological treatment
<0.3 → poorly biodegradable, may need chemical or advanced treatment

Other options:
খ) The water is not highly biodegradable; chemical treatment alone is not justified.
গ) BOD > COD is unusual, but here BOD < COD, so no error.
ঘ) COD indicates oxygen demand but does not alone reflect toxicity.

Exothermic reaction: The reaction releases heat. According to Le Chatelier’s principle, higher temperatures favor the reverse reaction, reducing equilibrium conversion.
Inter-stage cooling: Lowers the temperature between beds to shift equilibrium toward more SO₃ formation.
Multiple beds: Helps maintain a moderate temperature, ensuring high overall conversion without deactivating the catalyst.

Other options:
খ) H₂SO₄ decomposition occurs later; it’s not the reason for inter-stage cooling.
গ) Elemental sulfur formation is unrelated.
ঘ) Catalyst poisoning is mitigated by purification of SO₂, not cooling.

1.When sulfide ores (like ZnS, PbS, CuFeS₂) are roasted, SO₂ gas is produced.
2.Direct venting of SO₂ causes acid rain, so it is not allowed.
3.The Frasch process is used for extracting native sulfur from underground deposits, not for SO₂ control.
4.Neutralization with molten salts is technically possible but highly uncommon and expensive.
5.The most widely applied secondary environmental control is to convert SO₂ into H₂SO₄ in a contact process plant, which is both environmentally safer and economically valuable.

1.In the contact process, the key reaction is:
2SO₂+O₂⇌2SO₃ΔH=−196 kJ/mol
This is exothermic, so:
1.Lower temperature favors forward reaction (SO₃ formation).
2.But too low temperature reduces reaction rate (kinetically slow).
3.Higher temperature increases rate but shifts equilibrium backward.
2.Therefore, in practice, a compromise temperature (~450 °C) and a catalyst (V₂O₅) are used.
3.Even then, conversion never reaches 100% due to equilibrium limitations.

Other options:
Excess oxygen actually improves conversion, not limits it.
High SO₂ concentration at moderate T doesn’t fundamentally limit yield—equilibrium is the true bottleneck.
High pressure in absorption tower mainly affects SO₃ absorption in H₂SO₄, not the catalytic conversion yield.

1.Coal usually contains sulfur in the form of iron pyrite (FeS₂) and organic sulfur compounds
2.During combustion in power plants:
S  +  O₂ →  SO₂
3.The released SO₂ rises into the atmosphere, where it further oxidizes to SO₃ and reacts with water vapor to form H₂SO₄ (sulfuric acid).
4.This leads to acid rain, which damages ecosystems, soils, buildings, and human health.

Other options :
(ক) Coal does not just release elemental sulfur by evaporation.
(খ) Coal does not release large amounts of H₂S during normal combustion.
(গ) Not all sulfur stays in ash; the majority oxidizes and escapes as SO₂ gas.

1.The Claus process is used in refineries and gas plants to recover elemental sulfur from hydrogen sulfide (H₂S).
2.The process has two main steps:

1.Thermal stage:
H₂S+3/2O₂  →  SO₂+H₂O
(about one-third of H₂S is oxidized to SO₂).
2.Catalytic stages (multi-bed reactors):
2H₂S+SO₂ →  3S+2H₂O
This is exothermic and equilibrium-limited.
Cooling between beds and multiple catalytic passes are needed to shift equilibrium forward and maximize sulfur yield.
3.A single stage does not achieve complete conversion because equilibrium stops the reaction before all H₂S is consumed.
4.By using multiple catalytic beds with interstage cooling, conversion efficiency rises to 95–97%.
5.Tail-gas treatment can further increase sulfur recovery to >99%.

Other options:
(খ) Claus does not produce H₂SO₄ (that’s the contact process).
(গ) Sulfur’s boiling point isn’t a factor here.
(ঘ) Preventing SO₃ is important, but the main reason for multiple stages is to maximize sulfur recovery.

1.Urea is produced from ammonia (NH₃) and carbon dioxide (CO₂):
2NH₃+CO₂   →    NH₂COONH₄   →    (NH₂)₂CO+H₂O
2.In an ammonia plant (Haber–Bosch process), CO₂ is already generated as a by-product during natural gas reforming or other feedstock processing.
3.Instead of venting this CO₂, it is captured and directly used in urea production.
Advantages:
1. Greatly reduces the need for an external CO₂ supply.
2. Improves overall process integration and efficiency (NH₃ + CO₂ plants are often built together).
3. Cuts down on greenhouse gas emissions by utilizing CO₂ instead of releasing it.

Other options:
(ক) Urea already contains both N and C in fixed ratios; CO₂ use does not reduce nitrogen content.
(খ) Ammonium carbamate must form as an intermediate, it’s not prevented.
(ঘ) CO₂ does not directly increase ammonia synthesis rate (that depends on N₂ + H₂ equilibrium).

1.Urea plants in Bangladesh (e.g., at Ghorashal, Jamuna, Ashuganj, Shahjalal) are integrated with ammonia plants.
2.Urea synthesis involves very high pressure (≈150–250 bar) and high temperature (≈170–200 °C).
3.These conditions cause:
Severe corrosion (especially from carbamate solutions).
Risk of leakage from high-pressure equipment.
Potential explosion hazards if containment fails.

Other options:
(ক) Fluoride emissions are not related to urea granulation; this issue is seen in phosphate fertilizer plants.
(গ) Acidic effluent is a problem in TSP/DAP plants, not urea plants.
(ঘ)Elemental sulfur release is related to sulfuric acid or Claus plants, not urea.

1.Triple Superphosphate (TSP) is produced by reacting phosphate rock (apatite) with concentrated H₂SO₄:
Ca₁₀(PO₄)₆F₂+7H₂SO₄   →    3Ca(H₂PO₄)₂+7CaSO₄+2HF
2.This reaction is highly exothermic.
3.If temperature is not controlled:
Excessive heat can cause partial decomposition of phosphates.
Formation of slurry with unreacted acid, leading to acidic effluents in wash water.
Poor product quality (reduced P₂O₅ availability).

Other options:
(খ) Over-granulation is controlled during the granulation stage, not during acidulation.
(গ) CO₂ is not a major by-product of this reaction.
(ঘ) Ammonia absorption is related to urea or ammonium fertilizer plants, not TSP manufacture.

1.The Haber–Bosch process reaction is:
N₂+3H₂    ⇌    2NH₃ΔH=−92 kJ/mol
Exothermic → favored by low temperature.
Volume decreases (4 → 2 moles) → favored by high pressure.
2.Trade-off:
At very low temperature, equilibrium favors NH₃, but the reaction is too slow.
At very high temperature, the reaction is fast, but equilibrium shifts backward (less NH₃).
So, an optimum compromise is used:
Temperature: 400–500 °C
Pressure: 150–250 bar
Catalyst: Iron with promoters (K₂O, Al₂O₃, CaO, etc.)

Other options :
(খ) Room temp and 1 atm → reaction practically doesn’t proceed.
(গ) At 700 °C, equilibrium strongly disfavors NH₃ (decomposition).
(ঘ) At 200 °C and 20 bar, reaction is too slow to be industrially useful.

1.During TSP (Triple Superphosphate) production, phosphate rock contains fluorapatite (Ca₁₀(PO₄)₆F₂).
2.When treated with sulfuric acid, HF and SiF₄ gases are released:
Ca₁₀(PO₄)₆F₂+H₂SO₄    →    Ca(H₂PO₄)₂+HF+SiF₄
3.These fluorides dissolve in process water, creating acidic, fluoride-rich effluents.
Lime treatment works:
1.Lime (Ca(OH)₂) neutralizes acidity and precipitates fluoride as CaF₂ (insoluble solid):
2HF+Ca(OH)₂   →    CaF₂↓+2H₂O
2 This reduces fluoride concentration before discharge into rivers or soil.

Other options:
(ক) Burning phosphate rock does not eliminate fluoride release during acidulation.
(খ) Direct release into rivers causes severe water pollution and fish toxicity.
(গ) Ammonia scrubbing is used in DAP plants (NH₃-based), not TSP.

Solution: Adding lime (Ca(OH)₂):
1. Neutralizes the acidic effluent.
2. Precipitates fluoride as insoluble CaF₂, making it safe for disposal.

Other options:
Burning phosphate rock doesn’t prevent fluoride release.
Direct discharge contaminates rivers and soils.
Ammonia absorption is relevant to DAP plants, not TSP.

1.Molasses is the residual syrup left after sugar crystallization from sugarcane or sugar beet juice.
2.It is highly concentrated in sugars, but:
Most of the sucrose has already been crystallized, so it cannot be directly converted into white sugar.

Other options:
(ক) Ethanol fermentation – for bioethanol or industrial alcohol production.
(খ) Animal feed supplement – due to its high energy content.
(ঘ) Industrial alcohol production – e.g., for spirits, solvents, or biofuel.

1.Bagasse is the fibrous residue left after extracting juice from sugarcane.
2.Bangladeshi sugar mills commonly burn bagasse in boilers to generate steam and electricity, which:
Powers the sugar mill itself.
Reduces dependence on fossil fuels.
Improves overall energy efficiency and cost-effectiveness.

Other byproducts:
(ক) Molasses is typically used for ethanol fermentation, not burning.
(গ) Filter cake is mostly used as fertilizer (composting), not for energy.
(ঘ) Press mud (from sugarcane juice clarification) is generally used in soil amendment, not ethanol production.

Metallurgical coal (coking coal) requires:
Low volatile matter → to form strong coke.
Low to moderate ash → to minimize impurities in steel.
Sufficient fixed carbon → for heat and structural strength in coke.

Bangladeshi coal typically has:
High volatile matter → produces weak coke unsuitable for blast furnaces.
Moderate ash content → adds impurities to steel.

Other options:
(ক) Low sulfur content is actually desirable.
(খ) High fixed carbon would be good, not limiting.
(গ) Low moisture is beneficial for combustion efficiency.

1.Coal carbonization (coking) is the process of heating coal in the absence of air to drive off volatile components.
2.Direct products include:
Coke – a solid, carbon-rich material used extensively in metallurgy (especially in blast furnaces for iron and steel production).
Coal tar, ammonia, and light oils (byproducts).

Other options:
(খ) Fly ash is a byproduct of coal combustion, not carbonization.
(গ) Sulfur dioxide is produced during combustion, not direct carbonization.
(ঘ) Syngas (CO + H₂) is produced during gasification, not coking.

Bangladeshi coal has high volatile matter and moderate ash, making conventional combustion polluting (SO₂, particulates, CO₂).
IGCC involves:
1. Gasifying coal to produce syngas (CO + H₂).
2.Cleaning the syngas to remove particulates, sulfur, and other pollutants.
3.Using the syngas in a combined cycle power plant (gas turbine + steam turbine) for electricity generation.
Benefits:
1. Higher efficiency than traditional coal-fired plants.
2.Significantly reduces SO₂, NOₓ, and particulate emissions.

Other options:
(ক) Open combustion → highly polluting.
(খ) Direct landfilling → no energy recovery, environmental hazard.
(ঘ) Spontaneous combustion → uncontrolled, dangerous, and polluting.

1.Coal gasification converts coal into syngas (CO + H₂) for power, chemicals, or fuels.
2.Bangladesh has:
Significant coal reserves (e.g., Jamalganj, Barapukuria), so low reserves is not the main limitation.
Coal with high volatile matter, which is suitable for gasification.
3.The main challenges for large-scale projects are:
High capital cost for gasifiers, purification systems, and combined cycle power plants.
Advanced technology requirements and operational expertise.
Infrastructure for handling coal, syngas, and waste.

In Bangladesh, the largest portion of petroleum product consumption is for diesel, which is widely used in:
Transportation: buses, trucks, and other vehicles.
Power generation: diesel-based power plants, especially in rural or off-grid areas.
Other fuels like LPG, jet fuel, and furnace oil are significant in their respective sectors but represent smaller shares of total national petroleum consumption.

1.Reformate is produced from catalytic reforming of naphtha.
2.It has a high octane number, typically 90–100 RON, making it excellent for gasoline blending.

Other options:
Light naphtha: Low octane, usually used as feedstock for reforming rather than directly as gasoline.
Residual fuel oil: Heavy, low-octane, mainly for industrial burners.
Straight run diesel: Low octane, used in diesel engines, not gasoline.

1.Catalytic reforming converts naphthenes (cycloalkanes) into aromatics.
2.This reaction involves dehydrogenation, producing hydrogen gas as a byproduct:
Cyclohexane (naphthene)→Benzene (aromatic)+3H₂
​3.This hydrogen is then often recovered and used in hydrocracking units or hydrotreating processes.

Other options:
Methane from cracking → Not significant for hydrogen supply.
Hydrogen from steam reforming of natural gas → Used industrially, but not a byproduct of catalytic reforming.
Hydrogen from catalytic polymerization → Not a typical process in refineries.

Thermal cracking:
1.Uses high temperature and pressure to break large hydrocarbons into smaller ones.
2.Produces more unsaturated hydrocarbons and light gases.
3.Gasoline produced has lower octane.
Catalytic cracking:
1.Uses a catalyst at lower temperature and pressure.
2. Produces higher octane gasoline suitable for blending.
3.Gas yield (like LPG) is lower compared to thermal cracking, but the gasoline fraction is richer.

Other options:
ক) catalytic cracking produces gasoline as a main product, not only LPG.
খ) Catalytic cracking is mostly endothermic, not exothermic.
ঘ) Thermal cracking actually operates at higher temperatures and pressures than catalytic cracking.

1.Atmospheric distillation is performed at 1 atm pressure. It separates crude oil into light and middle fractions such as:
Gasoline, kerosene, diesel, and gas oil.
2.The heavier fractions (residuum) remain at the bottom.
3.Vacuum distillation is then used on the residuum to:
Prevent thermal cracking (coke formation) by distilling heavy fractions at lower pressures, which reduces boiling points.
Separate vacuum gas oil and vacuum residue.

Other options:
ক) Sulfur is not completely removed by distillation; it's removed later via hydrotreating.
গ) High-octane gasoline is produced later via reforming, not distillation.
ঘ) While vacuum distillation helps avoid coke, the main reason for atmospheric first is fraction separation and load reduction.

Fused silica glass is widely used for high-power UV laser optics because:
1.It has very low absorption in the UV range, allowing efficient transmission of laser light without heating.
2.It exhibits an extremely high laser-induced damage threshold, meaning it can withstand intense laser pulses without cracking or degrading.

Other options:
ক) Fused silica has a moderate refractive index; minimizing chromatic aberration is not its main advantage in high-power UV applications.
গ) Fused silica is virtually free of alkali ions, which actually improves UV resistance; alkali ions would be detrimental.
ঘ) It is optically isotropic; birefringence is minimal and not a reason for its preference.

Mullite (3Al₂O₃·2SiO₂) is a key phase in advanced ceramics because:
1.It has a high melting point (~1840 °C).
2.Exhibits low thermal expansion, excellent creep resistance, and high thermal stability, making it ideal for refractory and structural ceramics.

Other options:
ক) Mullite actually has low thermal expansion, not high.
খ) Mullite is refractory, not a flux.
গ)Mullite is crystalline, not amorphous; it does not promote glassy phase formation.

1.Tempered (toughened) glass is produced by rapidly quenching the surface of hot glass.
2.The surface cools and contracts faster than the interior, creating:
Compressive stress at the surface
Tensile stress in the interior
3.This stress profile significantly improves strength and resistance to crack propagation.

Other options:
ক)Glass is amorphous, no interlocking crystalline phase forms during tempering.
গ) Ion exchange strengthening (Na⁺ ↔ K⁺) is used in chemical toughening, not standard thermal tempering.
ঘ) Addition of TiO₂ affects optical/thermal properties but is not the main toughening mechanism.

Cement production in Bangladesh has shifted toward modern dry-process kilns because:
1.They are more energy-efficient than older wet-process kilns.
2.Preheaters and precalciners reduce fuel consumption and CO₂ emissions.

Other options:
ক) Most old plants used the wet process, but the trend is toward dry-process technology, not majority wet.
খ) Bangladesh produces a significant portion of its cement locally; it is not almost entirely imported.
গ)Most cement plants produce clinker locally; imported clinker is minimal.

1.The burning zone in a cement rotary kiln is typically around 1450 °C.
2.Operating above this temperature causes:
1. Over-sintering of clinker phases.
2. Incomplete reaction of CaO with SiO₂, resulting in excess free lime.
3.Excess free lime can:
1. Cause clinker expansion,
2.Lead to flash set when cement hydrates, compromising strength and durability.

Other options:
ক)Belite (C₂S) forms at lower temperatures; excessive temperature actually favors alite (C₃S) but may destabilize the clinker.
গ) High temperatures may increase fuel consumption due to heat loss, not improve efficiency.
ঘ) Gypsum addition depends on setting control, not directly reduced by high burning temperature.

1.Lime Saturation Factor (LSF) is defined as the ratio of available CaO to the amount required to combine with SiO₂, Al₂O₃, and Fe₂O₃ to form clinker minerals.
2.It controls the formation of key clinker phases:
Alite (C₃S): Provides early strength.
Belite (C₂S): Contributes to later strength.
3.Proper LSF ensures the clinker has optimal strength development.

Other options:
ক) Fineness and grindability are influenced by gypsum and clinker hardness, not LSF directly.
খ) Gypsum addition is for setting control, independent of LSF.
ঘ) Energy consumption during ball milling depends on clinker hardness and mill efficiency, not directly on LSF.

Mercury cell process:
1.Uses mercury as a cathode, leading to serious mercury pollution.
2.Produces caustic soda but with environmental hazards.
Membrane cell process:
1.Uses ion-selective membranes instead of mercury.
2.Produces high-purity NaOH (typically 30–35%) with no mercury emissions.
3.More environmentally friendly.

Other options:
খ)Membrane cells produce moderate-concentration NaOH, not necessarily higher than mercury cells, and energy consumption is comparable.
গ) Brine still needs purification to prevent membrane fouling.
ঘ) Membrane cells require electricity, so external power is necessary.

In the mercury cell process (also called the Castner-Kellner process):
1.Brine (NaCl solution) is electrolyzed.
2.At the cathode: Sodium ions are reduced on liquid mercury, forming a sodium-mercury amalgam.
3.This amalgam is then reacted with water in a separate chamber to produce sodium hydroxide (NaOH) and hydrogen gas.

Other options:
খ) Titanium/platinum is used in some modern anode materials for other electrolysis processes, not in mercury cells.
গ)Graphite electrodes are used as anodes in diaphragm cells, not as mercury cathodes.
ঘ) Porous asbestos diaphragms are used in diaphragm cell processes, not mercury cells.

In the Solvay process (used for producing soda ash, Na₂CO₃):
1.Ammonia is added to brine (NaCl solution).
This allows CO₂ to react preferentially with NH₃ + H₂O, forming ammonium bicarbonate (NH₄HCO₃).
2.The NH₄HCO₃ then reacts with NaCl in solution:
NaCl+NH₄HCO₃    →    NaHCO₃↓+NH₄Cl
3.precipitates because it is sparingly soluble, while ammonium salts remain dissolved.
4.On heating, NaHCO₃ decomposes to Na₂CO₃ (soda ash).
5.The ammonia is recovered and recycled, meaning it is not consumed — it behaves like a catalyst.

Other options:
ক) Ammonia does not directly form sodium carbonate.
খ) Brine (NaCl) dissolves in water, not in ammonia.
গ) CO₂ is supplied from limestone calcination, not from ammonia.

In chlor-alkali plants (producing NaOH, Cl₂, and H₂), the main environmental concerns are:

Mercury contamination → From older mercury cell process (liquid mercury cathode). Even trace leaks pollute water and sediments.
Chlorine gas emissions → Highly toxic and corrosive; leaks can cause serious local air pollution.
Wastewater disposal → Contains brine, chlorinated organics, and sometimes residual mercury or asbestos (from diaphragm cells).

Other options:
খ) CO₂ from limestone calcination is a concern in cement/lime industries, not chlor-alkali.
গ) SO₂ is linked to sulfuric acid plants, not chlor-alkali.
ঘ) Phosphate leaching is related to fertilizer industries, not chlor-alkali.

1.PVC in its rigid form is brittle, with poor impact resistance.
2.To improve toughness and flexibility:
Plasticizers (e.g., phthalates) are added → increase chain mobility, reduce brittleness.
Impact modifiers/elastomers (e.g., ABS, EVA, chlorinated polyethylene) are blended → improve impact strength by dissipating energy.

Other options:
ক) Higher molecular weight improves tensile strength but doesn’t significantly increase impact resistance.
খ) Syndiotactic vs. atactic PVC relates to stereoregularity; PVC is mostly atactic, but tacticity control is not the main factor for toughness.
গ) Increasing polymerization temperature doesn’t directly improve impact resistance; it may reduce polymer quality.

1.Polystyrene (PS) has a relatively high glass transition temperature (Tg ≈ 100 °C).
2.The reason is the presence of bulky phenyl (–C₆H₅) side groups attached to the polymer backbone.
These sterically hinder chain rotation and segmental mobility,
Making the polymer more rigid and raising Tg.
Other options:
খ) PS is amorphous, not highly crystalline.
গ) Chlorine atoms are present in PVC, not PS.
ঘ) Ordinary PS is not crosslinked; only special grades (e.g., thermoset resins) are.

HDPE (High-Density Polyethylene):
1.Chains are linear with very few branches.
2.This allows close packing, leading to high crystallinity (~70–90%).
3.Result → higher tensile strength, stiffness, and density.
LDPE (Low-Density Polyethylene):
1.Has a highly branched structure.
2.Branching prevents chains from packing closely, giving low crystallinity (~40–60%).
3.Result → lower tensile strength but higher flexibility.

Other options:
ক) Opposite is true: LDPE has more branching, not HDPE.
গ) Neither HDPE nor LDPE contains chlorine; that’s PVC.
ঘ) Both HDPE and LDPE are homopolymers of ethylene; the difference is in chain branching, not monomer type.

1.Rayon (viscose fiber) is produced by treating cellulose with carbon disulfide (CS₂) to form cellulose xanthate, which is then dissolved in caustic soda and spun into fibers.
2.The major hazard is:
Occupational: Workers exposed to CS₂ vapors may suffer from neurological, cardiovascular, and reproductive health issues.
Environmental: CS₂ is toxic, volatile, and contributes to air pollution.

Other options:
খ) Chlorine release can occur in pulp bleaching for paper, not the main rayon hazard.
গ) Mercury contamination is linked to chlor-alkali plants, not rayon.
ঘ) SO₂ emission comes from soda ash/sulfur industries, not rayon production.

Sulfite pulping process:
1. Uses sulfurous acid (H₂SO₃) and bisulfite salts.
2.Effluents contain soluble lignosulfonates and sulfur compounds.
3. These are biodegradable, but they cause high Biological Oxygen Demand (BOD) → depletion of dissolved oxygen in receiving waters.

Kraft pulping process:
1. Uses NaOH + Na₂S (alkaline).
2.Effluents are dark-colored, malodorous, and contain reduced sulfur compounds (TRS: H₂S, mercaptans).
3.However, lignin derivatives are less soluble, so BOD is lower than sulfite effluent.

Other options:
ক) sulfite effluent is actually more acidic.
গ) Chlorine-based bleaching can be an issue in both processes, but it’s not inherent to Kraft cooking liquor itself.
ঘ) the two processes differ significantly in effluent characteristics.

In the Kraft process, the recovery boiler is the heart of the chemical recovery system:
1. Black liquor (contains dissolved lignin + spent cooking chemicals) is concentrated and burned in the recovery boiler.
2. Functions:
Combusts organic matter (lignin residues) → produces heat.
Generates high-pressure steam → used for power and process heating.
Recovers inorganic pulping chemicals (mainly Na₂CO₃ and Na₂S) → sent to the causticizing cycle to regenerate NaOH.

Other options:
ক) Black liquor does not produce pulp; fibers are already separated earlier.
খ) Bleaching is a separate process, not done in the recovery boiler.
ঘ) Pulp water removal is done in washing, pressing, and drying stages, not in the recovery boiler.

Tallow (animal fat):
1. Rich in saturated long-chain fatty acids (mainly stearic and palmitic acids).
2. Produces a hard, durable soap with good cleansing but poor solubility and lather.

Coconut oil:
1. Rich in medium-chain fatty acids (mainly lauric acid).
2. Produces soap with excellent solubility and high lathering ability, even in hard or salty water.
By blending tallow and coconut oil, soap makers balance:
Hardness + durability (from tallow)
Foaminess + solubility (from coconut oil).

Other options:
খ) Saponification temperature is not significantly increased by coconut oil.
গ) Both yield glycerine during saponification; coconut oil doesn’t “compensate.”
ঘ) Free fatty acids are neutralized by alkali (NaOH/KOH), not coconut oil.

1.Phosphates (e.g., sodium tripolyphosphate, STPP) were widely used in detergents as builders.
2.When discharged into water bodies, phosphates act as nutrients → stimulate algal blooms (eutrophication).
3.This leads to oxygen depletion, harming aquatic life.

Other options:
ক) branched-chain surfactants (e.g., branched alkylbenzene sulfonates, BAS) are poorly biodegradable, which is why they were replaced by linear alkylbenzene sulfonates (LAS).
গ) Some synthetic detergents are non-biodegradable and persist in the environment.
ঘ) LAS are actually biodegradable and less toxic than branched analogs, so they are widely used.

Cold process soap-making:
1.Saponification occurs at lower temperatures.
2.Glycerine is retained in the soap, providing moisturizing properties.
3.Soap may require longer curing time to harden.
Hot process soap-making:
1.Saponification is accelerated by heating the mixture.
2.Glycerine is often separated and recovered as a by-product.
3. Produces soap faster but with less natural glycerine content.

Other options:
ক) Cold process soaps still usually require curing; they are not ready immediately.
খ) Higher temperatures describe the hot process, not cold.
ঘ) Acidification is a step in acid-alkali processes to recover fatty acids, not characteristic of cold vs. hot soap-making.

Pickling is a preparatory step in chrome tanning:
Hides are treated with acid (usually sulfuric acid) and salt.
The pH is lowered to ~2.5–3.0, which:
Swells the collagen fibers.
Makes them receptive to chromium(III) salts for efficient tanning.

Other options:
ক) Hair and epidermis removal occurs during liming and fleshing, before pickling.
গ) Drying is a later step, after tanning.
ঘ) Coloring occurs during dyeing or fatliquoring, not pickling.

Vegetable tanning uses plant-derived tannins (e.g., from oak, chestnut).
Pros: Produces firm, natural-looking leather with good aging properties.
Cons:
Slower process: Takes several days to weeks.
Less water-resistant than chrome-tanned leather.
Chrome tanning:
Uses chromium(III) salts.
Produces soft, flexible, and water-resistant leather in a shorter time.

Other options:
খ) Vegetable-tanned leather can be dyed.
গ) Chrome tanning is usually less environmentally friendly due to heavy metal residues.
ঘ) Vegetable-tanned leather is suitable for belts, saddles, and other sturdy items.

Chrome tanning uses chromium(III) salts (typically Cr₂(SO₄)₃) to stabilize collagen in hides.
The key reaction:
Cr³⁺ ions bind to carboxyl groups on collagen.
Forms cross-links between collagen fibers, increasing thermal stability, water resistance, and mechanical strength.

Other options:
ক) Covalent bonding with tannins occurs in vegetable tanning, not chrome tanning.
খ) Oxidation by air is not a tanning mechanism.
ঘ) Hydrolysis of collagen would degrade the protein, not stabilize it.

1.Deodorization is the final step in edible oil refining.
2.Purpose: Remove volatile compounds that cause unpleasant odor and taste, such as aldehydes, ketones, and short-chain fatty acids.
3.Oil is heated to high temperatures (180–250 °C) under vacuum.
4.Steam is passed through the oil, which strips away volatile odor-causing compounds.
5.Results in a neutral-flavored, odorless oil suitable for consumption.

Other options:
ক) Treating with activated charcoal → Part of bleaching, removes color and some impurities, not volatile odor compounds.
গ) Washing with hot water → Used in degumming or neutralization, not deodorization.
ঘ) Addition of antioxidants → Prevents oxidation and rancidity; does not remove odors.

1.Winterization (also called dewaxing) is a physical refining step applied to certain edible oils (like cottonseed, sunflower, and soybean oil) to prevent cloudiness at low temperatures.
Process:
1.Oil is chilled slowly to crystallize high-melting components (waxes, saturated triglycerides).
2.Crystals are filtered out, leaving a clear, cold-stable oil.

Other options:
ক) Reduce rancidity by hydrogenation → Hydrogenation modifies unsaturation; unrelated to winterization.
খ) Increase oil’s iodine value → Iodine value reflects unsaturation; winterization doesn’t affect it significantly.
ঘ) Increase oil’s calorific value → Calorific value remains essentially unchanged; winterization is about clarity and stability, not energy content.

Improve shelf life → Saturated or partially hydrogenated oils are less prone to oxidation and rancidity.
Modify texture → Converts liquid oils into semi-solid fats suitable for margarine, shortening, and bakery products.

Other options:
ক) Increase iodine value → Wrong; hydrogenation reduces iodine value because double bonds are saturated.
গ) Convert unsaturated fatty acids into saturated ones → Partially true, but this is the mechanism, not the primary purpose.
ঘ) Reduce calorific value → Wrong; hydrogenation does not significantly change calorific value.

Hard, durable, and glossy finish → Gives a smooth, reflective surface.
Moderate to quick drying → Depending on solvent and resin type.
Good adhesion → Suitable for metal, wood, and sometimes plastic surfaces.

Other options;
খ) High water solubility → Enamel paints are solvent-based, not water-soluble.
গ) Being made only from natural oils → Modern enamel paints often use synthetic resins, not just natural oils.
ঘ) Low adhesion → enamel paints are chosen for good adhesion and smooth finish.

Water-based → Uses water as a solvent/binder.
Matte finish → Provides a flat, non-reflective surface.
Economical and easy to apply → Mainly used for interior walls and ceilings.

Other options:
ক) Synthetic polymer-based → Refers to emulsion or acrylic paints, not traditional distemper.
খ) Solvent-based and quick-drying → Distemper is water-based, not solvent-based.
ঘ) Oil-based and glossy → Oil paints give glossy, durable finish, unlike matte distemper.

Common anti-corrosive pigments:
Red lead (Pb₃O₄) → Traditional anti-rust pigment.
Zinc chromate (ZnCrO₄) → Provides long-term protection by forming a passive layer on the metal.

Other options:
ক) Titanium dioxide → Provides whiteness and opacity, not corrosion protection.
গ) Ultramarine blue → Decorative pigment; no anti-corrosive property.
ঘ) Carbon black → Used for coloring and UV resistance, not for corrosion inhibition.