## States of Matter Questions and Answers Part-6

1. Longest mean free path under similar conditions of P and T stands for.
a) $N_{2}$
b) $O_{2}$
c) $H_{2}$
d) $CI_{2}$

Explanation: Mean free path $\propto \frac{1}{(Radius)^{2}}$

2. The mean free path ( $\lambda$ ) of a gas sample is given by
a) $\lambda=\sqrt{2\pi\sigma^{2}N}$
b) $\lambda=\frac{1}{\sqrt{2}.\pi\sigma^{2}N}$
c) $\lambda=\sqrt{2\pi\upsilon\sigma^{2}N}$
d) None of these

Explanation: Formula for mean free path is $\lambda=\frac{1}{\sqrt{2}.\pi\sigma^{2}N}$

3. Which of the following statements is false
a) Avogadro Number =$6.02 ×10^{21}$
b) The relationship between average velocity $\left(\overline{V}\right)$ and root mean square velocity (u) is $\left(\overline{V}\right)$ =.9213u
c) The mean kinetic energy of an ideal gas is independent of the pressure of the gass
d) The root mean square velocity of the gas can be calculated by the formula $\left(3RT/M\right)^{1/2}$

Explanation: Avogadro number is 6.023 * 1023

4. At higher altitude the boiling point of water lowers because
a) atmospheric pressure is low
b) temperature is low
c) atmospheric pressure is high
d) None of these

Explanation: At higher attitudes, boiling point is low because atmospheric pressure is low

5. Which of the following liquid will exhibit highest vapour pressure?
a) $C_{2}H_{5}OH\left(l\right)$
b) $NH_{3}\left(l\right)$
c) $HF\left(l\right)$
d) $H_{2}O\left(l\right)$

Explanation: The strength of H-bonding is in the order N....H < O....H < F....H

6. A manifestation of surface tension is :
a) rise of liquid in a capillary tube
b) spherical shape of liquid drops
c) upward movement of water in soils
d) All the above

Explanation: All the given phenomenon occurs due to surface tension

7. Generally , liquid drops assume spherical shape because:
a) a sphere has maximum surface area
b) a sphere has minimum surface area
c) sphere is symmetrical in shape
d) none of these

Explanation: Liquid drops assume spherical shape because a sphere has minimum surface area

8. On heating a liquid, its surface tension
a) increases
b) decreases
c) remains same
d) is reduced to zero

Explanation: Surface tension decreases with increase in temperature

9. Water drops stick to a glass surface due to:
a) cohesion
c) flocculation
d) None of these