This set of Class 11 Chemistry Chapter 2 Multiple Choice Questions & Answers (MCQs) focuses on “Towards Quantum Mechanical Model of the Atom”.

1. Who found out about dual behavior of a matter?

a) De Broglie

b) Bohr

c) Rutherford

d) Thomson

View Answer

Explanation: A French physicist named Louis de Broglie proposed that matter exhibits both particle and wave like nature. This means that like photons, electrons also should have both momentum and wavelength.

2. A ball of mass 0.5kg is moving with velocity 6.626 m/s. What’s the wavelength of that ball?

a) 1 x 10^{-34} m

b) 2 x 10^{-34} m

c) 2 x 10^{-32} m

d) 2 x 10^{-3} m

View Answer

Explanation: Louis de Brogie gave the realation between momentum and wavelength as λ = h/p. Here h is Planck’s constant, whose value is 6.626 x 10

^{-34}J/s. Wavelength = h/mv = 2 x 10

^{-34}m (momentum p = mass m x velocity v).

3. Mass of a photon is given by 3.313 x 10^{-34} kg. Find it’s wavelength.

a) 0.67A°

b) 0.67nm

c) 0.37A°

d) 1.67A°

View Answer

Explanation: Louis de Brogie gave the realation between momentum and wavelength as λ = h/p. Here h is Planck’s constant, whose value is 6.626 x 10

^{-34}J/s. Wavelength = h/mc = 6.626 x 10

^{-34}Js/(3.313 x 10

^{-34}kg x 3 x 10

^{8}m/s) = 0.67A°.

4. Determining the exact position and velocity of an electron is impossible at a time.

a) True

b) False

View Answer

Explanation: A German physicist, Werner Heisenberg stated Heisenberg’s principle of uncertainty, that states that determining the exact position and velocity of an electron is impossible at a time, as a result of dual nature of matter and radiation.

5. As per Heisenberg’s principle of uncertainty, the relation between relative momentum and relative position is __________

a) independent

b) equal

c) directly proportional

d) inversely proportional

View Answer

Explanation: Heisenberg’s principle of uncertainty states that the product of relative momentum and velocities is equal to greater than the h/4π, where is “h” is the Planck’s constant and is equal to 6.626 x 10

^{-34}Js.

6. The uncertainty of a ball is given by 0.5A°. Then calculate the uncertainty in momentum.

a) 2.055 x 10^{-24} kgm/s

b) 1.015 x 10^{-24} kgm/s

c) 1.055 x 10^{-24} kgm/s

d) 1.095 x 10^{-24} kgm/s

View Answer

Explanation: Heisenberg’s principle of uncertainty states that Δx. Δp ≥ h/4π, x is position, p is momentum and “h” is the Planck’s constant and is equal to 6.626 x 10

^{-34}Js. Relative momentum Δp = h/4πΔx = 1.055 x 10

^{-24}kgm/s.

7. If the uncertainties in position and momentum are equal, then the uncertainty in position is given by ____

a) √h/4π

b) √h4π

c) √h/4

d) √h/π

View Answer

Explanation: As we know, Heisenberg’s principle of uncertainty states that Δx. Δp ≥ h/4π, x is position, p is momentum and “h” is the Planck’s constant. Δx = Δp; Δx. Δx = h/4π; Δx = √h/4π

8. If the kinetic energy of an electron is 5J. Find out its wavelength.

a) 0.313 x 10^{15} m/s

b) 3.013 x 10^{15} m/s

c) 3.310 x 10^{15} m/s

d) 3.313 x 10^{15} m/s

View Answer

Explanation: We know that the mass of an electron is 9.1 x 10

^{-31}kg. Given that the kinetic energy of an electron is 5J. K.E = mv

^{2}/2 and by substituting we get v = √1.098 x 10

^{31}m/s = 3.313 x 10

^{15}m/s.

9. An object has a mass of 6 kg and velocity of 10 m/s. The speed is measured with 5% accuracy, then find out Δx in m.

a) 0.12676 x 10^{-34}

b) 0.1566 x 10^{-34}

c) 0.176 x 10^{-34}

d) 0.276 x 10^{-34}

View Answer

Explanation: Speed’s uncertainty is 10 x 5/100 = 0.5 m/s. We have Heisenberg’s principle of uncertainty i.e. Δx. Δp ≥ h/4π. Δx = h/2mπ. Therefore uncertainty in position = 6.626 x 10

^{-34}Js/12 x 3.1416 = 0.176 x 10

^{-34}.

10. Δx. Δp ≥ h/4π.

a) True

b) False

View Answer

Explanation: Heisenberg’s principle of uncertainty states that the product of relative momentum and velocities is equal to greater than the h/4π, where is “h” is the Planck’s constant and is equal to 6.626 x 10

^{-34}Js. Hence the above statement is true.

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