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৪৯তম বিসিএস ⎯ প্রাণ রসায়ন [৬০১]

পরীক্ষা৪৯তম বিসিএস ⎯ প্রাণ রসায়ন [৬০১]তারিখতারিখ অনির্ধারিতসময়17 minutes
মোট প্রশ্ন৩০
সিলেবাস
Exam 1 Biophysical Chemistry — Atom; Periodic property [Source: Class–1 and relevant books]
প্রশ্ন দেখুনঅনুশীলন
ঘনত্ব
উত্তর
উত্তরিতবর্তমানপুনরায় দেখুনঅসম্পূর্ণ

৪৯তম বিসিএস ⎯ প্রাণ রসায়ন [৬০১]

৪৯তম বিসিএস ⎯ প্রাণ রসায়ন [৬০১] · তারিখ অনির্ধারিত · ৩০ প্রশ্ন

১.
Which of the followings is not correct?
  1. ক
    νˉ= 1/λ​
  2. খ
    ν = c/λ​
  3. গ
    ΔE = h × ν
  4. ঘ
    ΔE ∝ λ
ব্যাখ্যা

E=hc/λ (Quantum theory of Max Plank)

২.
In Rutherford's a-scattering experiment what substance coated screen was used?
  1. ক
    PbS
  2. খ
    FeS
  3. গ
    ZnS
  4. ঘ
    CuS
ব্যাখ্যা

ZnS was used in that experiment

৩.
What is the value of Bohr's radius? 
  1. ক
    5.292×10−11 m
  2. খ
    2.18×10−18
  3. গ
    1312×10 kJ mol−1
  4. ঘ
    5.292×10−11A0
ব্যাখ্যা

৪.
Which pair is isotone?
  1. ক
    614​C, 714​N
  2. খ
    614​C, 618​C
  3. গ
    614​C, 816​O
  4. ঘ
    2964​Cu, 3064​Zn
ব্যাখ্যা

৫.
What is the value for mvr of an electron in 3rd energy level?
  1. ক
    nh/π​
  2. খ
     3h/2π
  3. গ
    nh/mΦ
  4. ঘ
    nrΔhµ
ব্যাখ্যা
​
৬.
Which light-ray has maximum frequency?
  1. ক
    X-ray
  2. খ
    UV-ray
  3. গ
    IR-ray
  4. ঘ
    Radio-waves
ব্যাখ্যা


(a) X-ray has lowest wave length, thus have highest frequency

৭.
What is the energy of radiated ray with wave-length 820 nm?
  1. ক
    2.424×10−19 J
  2. খ
    2.424×10−18 J
  3. গ
    24.24×10−19
  4. ঘ
    24.24×10−18 
ব্যাখ্যা
৮.
Wave-number (νˉ) of which rays is lowest? 
  1. ক
    X Ray
  2. খ
    UV
  3. গ
    IR
  4. ঘ
    Red Ray
ব্যাখ্যা
Ȳ=1/λ. So, Red ray have highest wave length thus have lowest wave number.
৯.
If E₁ is the energy of 1st orbit of H-atom, then what is its energy of 3rd orbit?
  1. ক
    E1​× (1/9)​
  2. খ
    E1​×​9
  3. গ
    E1​× (1/3)
  4. ঘ
    E1​×3
ব্যাখ্যা

১০.
In which Group rear earth elements are present?
  1. ক
    Group 1
  2. খ
    Group 2
  3. গ
    Group 3
  4. ঘ
    Group4
ব্যাখ্যা



Rare earth elements are a set of 17 chemical elements in the periodic table. They include the **lanthanide series** and the two elements that are chemically similar to them: **scandium** and **yttrium**.

Both scandium (Sc) and yttrium (Y) are located in **Group 3** of the periodic table, and the lanthanide series is typically shown as a separate block below the main table, but they are technically considered part of Group 3 as well. This is because these elements follow lanthanum (La), which is also in Group 3. Therefore, the rare earth elements are all associated with Group 3.

১১.
Which one is paramagnetic?
  1. ক
    Zn
  2. খ
    Cu
  3. গ
    Ca
  4. ঘ
    Mg
ব্যাখ্যা
Cu: [Ar]3d104s1. The single electron in the 4s orbital is unpaired.
১২.
Henry Moseley discovered a law relating X-ray frequencies to atomic numbers. Which of the following best captures the spirit of his discovery?
  1. ক
    Atomic weight determines all chemical and physical properties of an element.
  2. খ
    The frequency of characteristic X-rays depends on the square of the atomic number.
  3. গ
    The frequency of characteristic X-rays is proportional to the number of neutrons.
  4. ঘ
     Electrons emit X-rays only when moving between identical shells in different atoms.
ব্যাখ্যা

Moseley's Law is a principle in physics that relates the frequency of X-rays emitted by an atom to its atomic number. The law states that the square root of the characteristic X-ray frequency (ν) is directly proportional to the atomic number (Z) of the element. This can be expressed by the formula:

ν = k(Z−b)

১৩.
 If the square root of the frequency of Kα X-rays is plotted against atomic number Z, what does the graph look like?
  1. ক
    A parabola opening upwards.
  2. খ
    A straight line with a slope proportional to √a
  3. গ
    A hyperbola decreasing with Z
  4. ঘ
    A straight line passing through the origin.
ব্যাখ্যা
১৪.
Which of the following elements was placed correctly in the modern periodic table but incorrectly in Mendeleev’s table due to its atomic mass?
  1. ক
    Cobalt
  2. খ
    Nickel
  3. গ
    Tellurium
  4. ঘ
    Argon
ব্যাখ্যা
 Argon and Potassium had to be swapped when ordering by atomic number
১৫.
Which of the following statements about the periodic table is false?
  1. ক
     Ionization energy generally increases across a period.
  2. খ
    Atomic radius decreases across a period.
  3. গ
     Electronegativity decreases down a group.
  4. ঘ
    Metallic character increases across a period from left to right.
ব্যাখ্যা
(Correct: D — metallic character actually decreases across a period.)
১৬.
 Which of the following elements has the highest electronegativity?
  1. ক
    F
  2. খ
    O
  3. গ
    Cl
  4. ঘ
    N
ব্যাখ্যা

(Correct: A — Fluorine is the most electronegative element.)

১৭.
The difference between electronegativity and electron affinity is that:
  1. ক
    Electronegativity is measured in kJ/mol, electron affinity is unitless.
  2. খ
    Electronegativity is the tendency of an atom to attract electrons in a bond, while electron affinity is the energy change when an isolated atom gains an electron.
  3. গ
    Electronegativity depends only on atomic size, electron affinity depends only on nuclear charge.
  4. ঘ
    Both refer to the same property, just expressed in different units.
ব্যাখ্যা

১৮.
 If a gas has an initial pressure of 4 atm at 2 L, what will be the volume at 8 atm (constant temperature)?
  1. ক
    1L
  2. খ
    0.5L
  3. গ
    4L
  4. ঘ
    0.25L
ব্যাখ্যা

১৯.
Which of the following graphs represents Gay-Lussac’s law?
  1. ক
     P vs. 1/T (straight line)
  2. খ
     P vs. T (straight line)
  3. গ
    P vs. V (hyperbola)
  4. ঘ
     V vs. P (straight line)
ব্যাখ্যা

২০.
If 2 L of gas at 300 K is heated to 600 K at constant pressure, its volume will be:
  1. ক
    2L
  2. খ
    4L
  3. গ
    1L
  4. ঘ
    6L
ব্যাখ্যা

২১.
Avogadro’s law states that:
  1. ক
    Equal volumes of gases have equal mass at STP
  2. খ
    Equal volumes of gases contain equal numbers of molecules at the same temperature and pressure
  3. গ
    Equal masses of gases contain equal numbers of molecules
  4. ঘ
    Pressure is proportional to volume at constant temperature
ব্যাখ্যা

২২.
The SI unit of the universal gas constant R is:
  1. ক
     J mol−1K−1
  2. খ
    L atm mol−1 K−1
  3. গ
    Both A and B are correct units
  4. ঘ
    None of these
ব্যাখ্যা

২৩.
If P = 2 atm, V = 5 L, T = 300, T300 K, find n (R = 0.0821 L atm mol−1K−1).
  1. ক
    0.40 mol
  2. খ
    0.50 mol
  3. গ
     0.30 mol
  4. ঘ
    0.20 mol
ব্যাখ্যা

২৪.
The root mean square speed μ rms​ is proportional to:
  1. ক
    √(T\M)
  2. খ
    √(M\T)
  3. গ
    √(3T\M)
  4. ঘ
    T\M
ব্যাখ্যা

The formula for the root mean square (RMS) speed of gas molecules is c = √(3RT/M)

২৫.
If temperature is doubled, the average kinetic energy:
  1. ক
    Doubles
  2. খ
    Triples
  3. গ
    Quadruples
  4. ঘ
    Remain same
ব্যাখ্যা

(Correct: A — KE∝T
২৬.
Dalton's Law of Partial pressure fails when
  1. ক
    Gas are not ideal gas
  2. খ
    Gases reacts each other
  3. গ
    Have very low density
  4. ঘ
    Above critical temperature
ব্যাখ্যা

Reaction among gases disrupts the relation of Partial Pressure

২৭.
Which of the following gases will have the largest a value in the Van Der Waals Equation?
  1. ক
    He
  2. খ
    CO2
  3. গ
    N2
  4. ঘ
    H2
ব্যাখ্যা

(Correct: B — stronger intermolecular forces)
২৮.
The term (V−mb) in the equation of real gas accounts for:
  1. ক
     Increase in kinetic energy
  2. খ
    Pressure correction
  3. গ
    Increase in temperature
  4. ঘ
    Free volume available for molecular motion
ব্যাখ্যা

২৯.
The line obtained from the Boyle's Law known as 
  1. ক
    isobar
  2. খ
    isotherm
  3. গ
    isomolar
  4. ঘ
    isotope 
ব্যাখ্যা

Boyle's Law works at constant temperature and graph known a isotherm

৩০.
The idea of absolute Zero temperature came from:
  1. ক
    Boyle's Law
  2. খ
    Avogadro's Law
  3. গ
    Charles Law
  4. ঘ
    Calvin's Law
ব্যাখ্যা

Herein, Charles Law states that the volume of a gas reaches at -273 degree Celsius or 0K. This indicate the absolute Zero Temperature.