Avengers academy
subject - Chemistry Total Marks : 25
MINOR TEST - 3
* Choose The Right Answer From The Given Options.[1 Marks Each] [25]
1. The first line in the Balmer series in the H atom will have the frequency:
(A) 3.29 × 1025 s-1 (B) 4.57 × 1024 s-1
(C) 8.22 × 1025 s-1 (D) 8.02 × 1014 s-1
Ans. :
b. 4.57 × 1024 s-1
Explanation:
Frequency of first line in Balmer series can be calculated as,
15 1 1 −1
v = 3.29 × 10 [ 2
− 2
]s
n n
2 2
Here, n1 = 2 ⇒ n2 = 3
15 5
= 3.29 × 10 ×
36
14 −1
= 4.57 × 10 s .
2. Identify the correct order of increase in the energy of the orbitals for hydrogen
atom:
(A) 1s < 28 = 2p < 3s = 3p = 3d < 4s = 4 p = 4d = 4f
(B) 1s > 2s = 2p > 3s = 3p = 3d > 4s = 4p = 4d = 4f
(C) 1s = 2s = 3s = 4s > 2p = 3 p = 4p > 3d = 4d > 4f
(D) 1s = 2s = 3s = 4s < 2p = 3p = 4p < 3d = 4d < 4f
Ans. :
a. 1s < 28 = 2p < 3s = 3p = 3d < 4s = 4 p = 4d = 4f
3. Which of the following properties of atom could be explained correctly by
Thomson Model of atom?
(A) Overall neutrality of atom. (B) Spectra of hydrogen atom.
(C) Position of electrons, protons and (D) Stability of atom.
neutrons in atom.
Ans. :
a. Overall neutrality of atom.
Explanation:
According to Thomson model of atom, the mass of the atom is assumed to
be uniformly distributed over the atom. This model was able to explain the
overall neutrality of the atom.
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4. The electronic transition from n = 2 to n = 1 will produce the shortest
wavelength in (where, n = principal quantum number).
(A) He+ (B) H (C) H+ (D) Li2+
Ans. :
d. Li2+
Explanation:
The electronic transition from n = 2 to n = 1 will produce the shortest
wavelength in Li2+. The exact value can be calculated via Rydberg formula,
1
( ∵ Z ∝ )
λ
5. The series of lines appearing in UV region of electromagnetic spectrum of
hydrogen is called:
(A) Bracket series. (B) Pfund series.
(C) Lyman series. (D) Paschen series.
Ans. :
c. Lyman series.
6. The de Broglie wavelengths associated with a ball of mass 1kg having kinetic
energy 0.5J is:
(A) 6.626 × 10-34m (B) 13.20 × 10-34m (C) 10.38 × 10-21m (D) 6.626 × 10-34A
Ans. :
a. 6.626 × 10-34m
Explanation:
λ =
h
mv
and K.E. = 1
2
mv
2
2 2KE
v =
m
−−−−−
KE×2
⇒ v = √
m
h
λ =
2KE
m√
m
−34
h 6.626×10
= =
√2KE×m √2×0.5×1
−34
= 6.626 × 10 m
7. Bohr proposed his atomic model based on:
(A) Oil drop experiment.
(B) Planck's quantum theory.
(C) x-ray scattering experiment.
(D) Experiments on conduction of gases.
Ans. :
b. Planck's quantum theory.
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Explanation:
Bohr proposed his atomic model based on planck's quantum theory.
8. The phenomenon of splitting of spectral lines under the influence of the electric
field is called:
(A) Stark effect. (B) Photoelectric effect.
(C) Zeeman effect. (D) Electromagnetic effect.
Ans. :
a. Stark effect.
9. The maximum number of electrons that can be filled into all the orbitals
corresponding to the azimuthal quantum number l = 3, is:
(A) 14 (B) 15 (C) 12 (D) 18
Ans. :
a. 14
Explanation:
For l = 3, possible values of m = 2l + 1 = 7. For each m, there can be 2
electrons filled.
Maximum number of electrons, thus = 2 × 7 = 14.
10. How many electrons can fit in the orbital for which:
n = 3 and l = 1?
(A) 10 (B) 14 (C) 2 (D) 6
Ans. :
d. 6
11. How many lines does a spectrum contain in an electronic transition from n = 1
to n = 5 in hydrogen atom?
(A) 10 (B) 8 (C) 1 (D) 5
Ans. :
a. 10
Explanation:
The no. of spectral lines produced in a spectrum=
(n2 − n1 )(n2 − n1 +1)
Given that n2 = 5 and n1= 1; the no. of spectral lines =
4×5
= 10.
12. The number of radial nodes for 3p orbital is __________.
(A) 3. (B) 4. (C) 2. (D) 1.
Ans. :
d. 1.
Explanation:
Number of radial nodes = n - 1 - 1
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For 3p orbital, n = 3 - 1 - 1 = 1
Number of radial nodes = 3 - 1 - 1 = 1.
13. Which of the following is the energy of a possible excited state of hydrogen?
(A) +13.6eV (B) -6.8eV (C) -3.4eV (D) +6.8eV
Ans. :
c. -3.4eV
14. The first model of an atom was given by _____________.
(A) N. Bohr (B) E. Goldstein (C) Rutherford (D) J.J. Thomson
Ans. :
d. J.J. Thomson
Explanation:
Sir J.J Thomson gave the first model of atom.
He by means of cathode-ray experiment discovered the existence of
negatively charged particles in an atom which led to the discovery of
electrons.
He gave the plum-pudding model of an atom in which electrons are
embedded in atom-like currants.
Positive electrons are distributed all over the atom.
15. Identify the pairs which are not of isotopes?
(A) 13
6
X,
13
6
Y. (B) 35
17
X,
37
17
Y. (C) 14
6
X,
14
7
Y. (D) 8
4
X,
8
5
Y.
Ans. :
c. 14
6
X,
14
7
Y.
d. 8
4
X,
8
5
Y.
Explanation:
Isotopes have the same atomic number but different mass number.
∴ (
14
6
X,
14
7
Y) and (
8
4
X,
8
5
Y) are not isotopes.
16. A ray of white light is spread out into a series of coloured bands of visible light
are called:
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(A) Visible band. (B) Spectrum.
(C) Electronic spectrum. (D) None of these.
Ans. :
b. Spectrum.
17. On bombarding a beam of a-particles on the atom of the gold sheet, a few
particles get deflected whereas most of them go straight and remains
undeflected. This is due to:
(A) The nucleus occupy much smaller volume as compared to the volume of atom.
(B) The force of repulsion on fast moving a-particles is very small.
(C) The neutrons in the nucleus do not have any effect on a-particles.
(D) The force of attraction on a-particles by the oppositely charged electron is not
sufficient.
Ans. :
a. The nucleus occupy much smaller volume as compared to the volume of
atom.
Explanation:
On bombarding a beam of a-particles on the atom of the gold sheet, a few
particles get deflected whereas most of them go straight and remains
undeflected because the nucleus occupy much smaller volume as compared
to the volume of atom.
18. What tool was Thomson using when he discovered the electron?
(A) Magnifying Glass (B) Hammer
(C) Cathode Ray (D) Microscope
Ans. :
c. Cathode Ray
19. The radius of which of the following orbit is same as that of first orbit of
hydrogen atom?
(A) He+(n = 2) (B) L2+(n = 2) (C) Li2+(n = 3) (D) Be3+(n = 2)
Ans. :
d. Be3+(n = 2)
Explanation:
˚ 2 2
0.529 A× n 0.529×1
rn = =
z 1
= 0.529Å for H-atom
˚ 2 ˚ 2
3+ 0.529 A× 2 0.529 A× 2
Be = =
z 4
˚
= 0.529A
20. Thomson proposed the model of an atom similar to:
(A) Christmas tree. (B) Christmas pudding.
(C) Chocolate. (D) None of the above.
Ans. :
b. Christmas pudding.
Explanation:
Thomson proposed the model of an atom be similar to that of a Christmas
pudding. The electrons in a sphere of positive charge were like currants (dry
fruits) in a spherical Christmas pudding.
21. Protons and neutrons are also called __________.
(A) Nucleons (B) Isotope (C) Isobars (D) Elements
Ans. :
a. Nucleons
Explanation:
Protons and neutrons are also called nucleons.
22. The radius of second Bohr's orbits for hydrogen atoms is:
−34 −31 19C
h = 6.6262 × 10 Js, me = 9.109 × 10 kg, echange = 1.6021 × 10
(A) 1.65A
˚
(B) 4.76A
˚
(C) 0.529A
˚
(D) 2.12A
˚
Ans. :
d. ˚
2.12A
Explanation:
2 2
n h
rn = 2 2
4π me Z
We get, r
˚ 2 ˚ 2
0.529 A× 2 0.529 A× 2
n = =
z 4
˚
= 2.12A
23. Total number of orbitals associated with third shell will be __________.
(A) 2. (B) 4. (C) 9. (D) 3.
Ans. :
c. 9.
Explanation:
No of orbitals in 3rd shell (n = 3) = n2 = 32 = 9.
24. The value of 'h' = 6.63 × 10-34Js. The speed of light is 3 × 1017nm/ s-1. Which
value is closer to the wavelength in nanometer of a quantum of light with
frequency 6 × 1015s-1.
(A) 50 (B) 75 (C) 10 (D) 25
Ans. :
a. 50
Explanation:
c
v =
λ
17 −1
3×10 m/ ms
⇒
c
v
=
15 −1
= 50nm.
6×10 n/ ms
25. Who was the first scientist to propose a model for the structure of an atom?
(A) J.J. Thomson (B) Dalton
(C) Ernest Rutherford (D) E. Goldstein
Ans. :
a. J.J. Thomson
Explanation:
J.J. Thomson was the first one to propose a model for the structure of an
atom.
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