## States of Matter Questions and Answers Part-5

1. An ideal gas is one which obeys the gas laws under
a) a few selected experimental conditions
b) all experimental conditions
c) low pressure alone
d) high temperature alone

Explanation: An ideal gas obeys the gas laws under all experimental conditions

2. The temperature at which real gases obey the ideal gas laws over a wide range of pressure is called
a) Critical temperature
b) Boyle’s Temperature
c) Inversion temperature
d) Reduced temperature

Explanation: Boyle’s temperature by definition. At this temperature the real gases obey ideal gas laws over wide range of P.

3. Which of the following exhibits the weakest inter- molecular forces
a) $NH_{3}$
b) HCl
c) He
d) $H_{2}O$

Explanation: "He" possess van der waals forces of attraction, which are weak in nature

4. The van der Waal’s equation reduces itself to the ideal gas equation at
a) high pressure and low temperature
b) low pressure and low temperature
c) low pressure and high temperature
d) high pressure alone

Explanation: At low pressure and high temperature terms a and b are negligible hence PV = nRT

5. An ideal gas obeying kinetic theory of gases can be liquefied if
a) its temperature is more than critical temperature $T_{C}$
b) its pressure is more than critical pressure $P_{C}$
c) its pressure is more than $P_{C}$ at a temperature less than $T_{C}$
d) it cannot be liquefied at any value of P and T

Explanation: Ideal gas cannot be liquefied at any value of P and T since there are no intermolecular interactions between molecules

6. The ratio of Boyle’s temperature and critical temperature for a gas is
a) $\frac{8}{27}$
b) $\frac{27}{8}$
c) $\frac{1}{2}$
d) $\frac{2}{1}$

Explanation: Boyle’s temperature, $T_{b}=\frac{a}{Rb}$  and critical temperature, $T_{c}=\frac{8a}{27Rb}$
$\frac{T_{b}}{T_{c}}=\frac{27}{8}$

7. The value of van der waals constant ‘a’ for gases   $O_{2},N_{2},NH_{3} andCH_{4}$    are 1.360, 1.390, 4.170 and $2.253 liter^{2}$  atm mol–2 respectively. The gas which can most easily beliquefied is
a) $O_{2}$
b) $N_{2}$
c) $NH_{3}$
d) $CH_{4}$

Explanation: The higher the value of ‘a’, more the value of Tc , easy is the liquefaction

8. Joule- Thomson coefficient $\left(\frac{\delta T}{\delta P}\right)_{H}$ for an ideal gas is
a) zero
b) positive
c) negative
d) None of these

Explanation: Ideal gas does not exhibit Joule Thomson effect. Hence $\left(\frac{\delta T}{\delta P}\right)_{H}$ , the Joule-Thomson coefficient is zero

9. The inversion temperature $\left(T_{i}\right)$ for a gas is given by
a) a / Rb
b) 2a / Rb
c) $\frac{Rb}{a}$
d) $\frac{2Rb}{a}$

Explanation: Ti = $\frac{2a}{Rb}$ Where Ti is inversion temperature.