CBSE Class 11 Chemistry Structure of Atom MCQs Set B

Question: The Bohr orbit radius for the hydrogen atom (n = 1) is approximately 0.530 Å. The radius for the first excited state (n = 2) orbit is (in Å)
a) 4.77
b) 1.06
c) 0.13
d) 2.12
Answer: d

Question: The ion that is isoelectronic with CO is
a) CN^–
b) N^{2 +}
c) O^2–
d) N^{2 –} 
Answer: a

Question: According to law of photochemical equivalence the energy absorbed (in ergs/mole) is given as (h = 6.62 × 10^–27 ergs, c = 3 × 1010 cm s^–1, NA = 6.02 × 10²³ mol^–1)
a) 1.196 ×10⁸λ
b) 2.859 10⁵ ×λ
c) 2.859 ×10¹⁶λ
d) 1.196 ×10₁₆λ
Answer: a

Question: The frequency of radiation emitted when the electron falls from n = 4 to n = 1 in a hydrogen atom will be (Given ionization energy of H = 2.18 × 10^–18 J atom^–1 and h = 6.626 × 0^–34 J s)
a) 1.54 × 10¹⁵ s^–1
b) 1.03 × 10¹⁵ s^–1
c) 3.08 × 10¹⁵ s^–1
d) 2.00 × 10¹⁵ s^–1 
Answer: c

Question: The energies E₁ and E₂ of two radiations are 25 eV and 50 eV respectively. The relation between their wavelengths i.e., λ₁ and λ₂ will be
a) λ₁ = λ₂
b) λ₁ = 2λ₂
c) λ₁ = 4λ₂
d) λ₁=1/2 λ₂ 
Answer: b

Question: If uncertainty in position and momentum are equal, then uncertainty in velocity is
a) 1/m √h π
b) √ h π
c) 1 /2m √h π
d) √h2π 
Answer: c

Question: The number of protons, neutrons and electrons in ¹⁷⁵₇₁Lu, respectively, are
a) 71, 104 and 71
b) 104, 71 and 71
c) 71, 71 and 104
d) 175, 104 and 71
Answer: a

Question: A 0.66 kg ball is moving with a speed of 100 m/s. The associated wavelength will be (h = 6.6 × 10^–34 J s)
a) 6.6 × 10^–32 m
b) 6.6 × 10^–34 m
c) 1.0 × 10^–35 m
d) 1.0 × 10^–32 m
Answer: c 

Question: The uncertainty in momentum of an electron is 1 × 10^–5 kg m/s. The uncertainty in its position will be (h = 6.62 × 10^–34 kg m²/s)
a) 5.27 × 10^–30 m
b) 1.05 × 10^–26 m
c) 1.05 × 10^–28 m
d) 5.25 × 10^–28 m 
Answer: a

Question: Who modified Bohr’s theory by introducing elliptical orbits for electron path?
a) Rutherford
b) Thomson
c) Hund
d) Sommerfeld 
Answer: d

Question: The value of Planck’s constant is 6.63 × 10^–34 Js. The speed of light is 3 × 10¹⁷ nm s^–1. Which value is closest to the wavelength in nanometer of a quantum of light with frequency f 6 × 10¹⁵ s^–1?
a) 50 
b) 75
c) 10
d) 25
Answer: a

Question: In a Bohr’s model of an atom, when an electron jumps from n = 1 to n = 3, how much energy will be emitted or absorbed?
a) 2.389 × 10^–12 ergs
b) 0.239 × 10^–10 ergs
c) 2.15 × 10^–11 ergs
d) 0.1936 × 10^–10 ergs
Answer: d

Question: The energy of second Bohr orbit of the hydrogen atom is –328 kJ mol^–1; hence the energy of fourth Bohr orbit would be
a) – 41 kJ mol^–1
b) –82 kJ mol^–1
c) –164 kJ mol^–1
d) –1312 kJ mol^–1 
Answer: b

Question: Be²⁺ is isoelectronic with which of the following ions?
a) H⁺
b) Li⁺
c) Na⁺
d) Mg²⁺ 
Answer: b

Question: Which one of the following is not isoelectronic with O₂–?
a) Tl⁺
b) Na⁺
c) N^3–
d) F^–
Answer: a

Question: According to the Bohr theory, which of the following transitions in the hydrogen atom will give rise to the least energetic photon?
a) n = 6 to n = 1
b) n = 5 to n = 4
c) n = 6 to n = 5
d) n = 5 to n = 3
Answer: c

Question: The spectrum of He is expected to be similar to that
a) H
b) Li⁺
c) Na
d) He⁺ 
Answer: b

Question: Calculate the energy in joule corresponding to light of wavelength 45 nm. (Planck’s constant, h = 6.63 × 10^–34 J s, speed of light, c = 3 × 108 m s^–1)
a) 6.67 × 10¹⁵
b) 6.67 × 10¹¹
c) 4.42 × 10^–15
d) 4.42 × 10^–18
Answer: d

Question: Given : The mass of electron is 9.11 × 10^–31 kg, Planck constant is 6.626 × 10^–34 J s, the uncertainty involved in the measurement of velocity within a distance of 0.1 Å is
a) 5.79 × 10⁵ m s^–1
b) 5.79 × 10⁶ m s^–1
c) 5.79 × 10⁷ m s^–1
d) 5.79 × 10⁸ m s^–1
Answer: b

Question: In hydrogen atom, energy of first excited state is –3.4 eV. Then find out K.E. of same orbit of hydrogen atom.
a) +3.4 eV
b) +6.8 eV
c) –13.6 eV
d) +13.6 eV 
Answer: a

Question: The de Broglie wavelength of a particle with mass 1 g and velocity 100 m/s is
a) 6.63 × 10^–35 m
b) 6.63 × 10^–34 m
c) 6.63 × 10^–33 m
d) 6.65 × 10^–35 m
Answer: c

Question: The position of both, an electron and a helium atom is known within 1.0 nm. Further the momentum of the electron is known within 5.0 × 10^–26 kg m s^–1. The minimum ncertainty in the measurement of the momentum of the helium atom is
a) 8.0 × 10^–26 kg m s^–1
b) 80 kg m s^–1
c) 50 kg m s^–1
d) 5.0 × 10^–26 kg m s^–1
Answer: d

Question: What will be the longest wavelength line in Balmer series of spectrum?
a) 546 nm
b) 656 nm
c) 566 nm
d) 556 nm
Answer: b

Question: The value of Planck’s constant is 6.63 × 10^–34 J s. The velocity of light is 3.0 × 10⁸ m s^–1. Which value is closest to the wavelength in nanometers of a quantum of light with requency of 8 × 1015 s^–1 ?
a) 2 × 10^–25
b) 5 × 10^–18
c) 4 × 10¹
d) 3 × 10⁷
Answer: c

Question: Which of the following series of transitions in the spectrum of hydrogen atom falls in visible region?
a) Brackett series
b) Lyman series
c) Balmer series
d) Paschen series
Answer: c

Question: The radius of hydrogen atom in the ground state is 0.53 Å. The radius of Li²⁺ ion (atomic number = 3) in a similar state is
a) 0.53 Å
b) 1.06 Å
c) 0.17 Å
d) 0.265 Å 
Answer: c

Question: The measurement of the electron position is associated with an uncertainty in momentum, which is equal to 1 × 10^–18 g cm s^–1. The uncertainty in electron velocity is (mass of an lectron is 9 × 10^–28 g)
a) 1 × 10⁵ cm s^–1
b) 1 × 10¹¹ cm s^–1
c) 1 × 10⁹ cm s^–1
d) 1 × 10⁶ cm s^–1 
Answer: c

Question: If r is the radius of the first orbit, the radius of nth orbit of H-atom is given by
a) rn²
b) rn
c) r/n
d) r2n²
Answer: a

Question: For given energy, E = 3.03 × 10^–19 joules corresponding wavelength is (h = 6.626 × 10^–34 J sec, c = 3 × 10⁸ m/sec)
a) 65.6 nm
b) 6.56 nm
c) 3.4 nm
d) 656 nm 
Answer: d

Question: Isoelectronic species are
a) CO, CN–, NO+, C₂ ^2–
b) CO–, CN, NO, C₂ –
c) CO+, CN+, NO–, C₂
d) CO, CN, NO, C₂ 
Answer: a