Fifth Chapter Solved Exercise MCQs Of FSc First Year Chemistry

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Fifth chapter solved MCQs with explanation

1: The nature of positive rays depends on:

  1. The nature of electrode
  2. The nature of discharge tube
  3. The nature of residual gas
  4. All of the above

Explanation

When high speed cathode rays strike the molecules of a gas enclosed in a discharge tube, they knock out the electrons from the gas molecules and positive rays are produced. Thus, the nature of positive rays depends upon the nature of the residual gas.

First Chapter Solved Exercise MCQs Of FSc First Year Chemistry

Second Chapter Solved Exercise MCQs Of FSc First-Year Chemistry

2: The velocity of photon is:

  1. Independent of its wavelength
  2. Depends on its wavelength
  3. Equal to square of its amplitude
  4. Depends on its source

Explanation

The photons of all the wavelengths have the same velocity. These photons may be of radio frequency regions are X-rays. option (1) is correct.

3: The wave number of the light emitted by a certain source is 2 x 106 m. The wavelength of this light is

  1. 500 nm
  2. 500 m
  3. 200 nm
  4. 5 x 107 m

Explanation:

Wave number

v͞ =2×106 m-1

Wavelength

Lamda =?

Applying formula;

Lamda = 1/v =1/2×106 m-1

Lamda =5×10-7 m

Lamda =500×10-9 m

Since, 10-9 m =1 nm

Thus, 500×10-9 m =500 nm So, option (1) is correct.

4: Rutherford’s model of atom failed because:

  1. The atom did not have a nucleus and electrons
  2. It did not account for the attraction between photons and neutrons
  3. It did not account for the stability of atom
  4. There is actually no space between the nucleus and the electrons

Explanation:

Rutherford’s model cannot account for the stability of atom. According to this model, the outermost electrons could not be stationary. If they were, they would gradually be attracted by the nucleus till they fall into it but for stable atomic structure the electrons were supposed to be moving around the nucleus in closed orbit. The centrifugal force keeps the nuclear force balanced.

5: Bohr’s model of atom is contradicted by:

  1. Plank quantum theory
  2. Pauli exclusion principle
  3. Heisenberg’s uncertainty principle
  4. All of the above

Explanation:

Bohr is certain about the position of the electron in an orbit according to his postulate. This contradicts the Heisenberg’s uncertainty principle. Option (3) is correct.

6: Splitting of spectral lines when atoms are subjected to strong electric field is called:

  1. Zeeman effect
  2. Stark effect
  3. Photoelectric effect
  4. Compton effect

Explanation:

The splitting of spectral lines in electric field was studied by Stark. Option (b) is correct.

7: In the ground state of an atom, the electron is present:

  1. In the nucleus
  2. In the second shell
  3. Nearest to the nucleus
  4. Farthest to the nucleus

Explanation

In the ground state of an atom, the electron is always present in the lower energy level and this lower energy level is always nearest to the nucleus. So, option (3) is correct.

8: Quantum number value for 2p orbitals are:

  1. n =2, l =1
  2. n =1, l =2
  3. n =1, l =0
  4. n =2, l =0

Explanation:

In 2p, the digit 2 stands for principle quantum number. For p- orbital the value of azimuthal quantum number ‘l’ is 1.so, option (1) is correct.

9: when 6d orbital is complete, the entering electron goes into:

  1. 7f
  2. 7s
  3. 7p
  4. 7d

Explanation:

According to the Auf-Bau’s principle, the electrons should be filled in energy sub-shells in the order of increasing energy values. According to the energy level diagram when 6d orbital is complete, the entering electron will go into 7p.Hence, option (3) is correct.

10: Orbitals having the same energy are called;

  1. Hybrid orbitals
  2. Valence orbitals
  3. Degenerate orbitals
  4. d- orbitals

Explanation:

Orbitals having the same energy are called degenerate orbitals. So, option (3) is correct.