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

Discussion

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

Discussion

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) \[H_{2}O\]

Discussion

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

Discussion

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

Discussion

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) \[\frac{2}{1}\]

Discussion

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) \[CH_{4}\]

Discussion

Explanation: The higher the value of ‘a’, more the value of T

_{c}, 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

Discussion

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) \[\frac{2Rb}{a}\]

Discussion

Explanation: T

_{i}= \[\frac{2a}{Rb}\] Where T

_{i}is inversion temperature.

10. The Joule-Thomson coefficient for a gas is zero at

a) Inversion temperature

b) Critical temperature

c) Absolute temperature

d) Below 0ºC

Discussion

Explanation: At exact inversion temperature there is neither heating nor cooling or no Joule Thomson effect