The mean free path ($\mathrm{\lambda }$) of a gas sample is given by:

1. $\lambda =\sqrt{2}\pi {\sigma }^{2}N$                               

2. $\lambda =1/\sqrt{2}\pi {\sigma }^{2}N$

3. $\lambda =\sqrt{2}\pi \mu {\sigma }^{2}N$                               

4. none of these

Which is lighter than dry air?

1. Moist air                             

2. SO₂

3. Cl₂                                      

4. O₂

The ratio a/b (the terms used in van der Waals' equation) has the unit-

1. atm litre mol^-1                           

2. atm dm³ mol^-1

3. dyne cm mol^-1                           

4. All of the above

The maximum deviation from ideal gas behaviour takes place -  

1. At high temperature and low pressure.

2. At low temperature and high pressure.

3. At high temperature and high pressure.

4. At low temperature and low pressure.

Joule-Thomson coefficient ($\partial \mathrm{T}/\partial \mathrm{P}$)_H for an ideal gas is:

1. zero                                 

2. +ve

3. -ve                                   

4. none of these

All the three states H₂O, i.e., the triple point for H₂O the equilibrium,

                       Ice $\rightleftharpoons$Water$\rightleftharpoons$Vapour exist at:

1. 3.85 mm and 0.0981 $°$C

2. 4.58 mm and 0.0098 $°$C

3. 760 mm and 0$°$C

4. none of the above

The unit of van der Waals' constant 'b' is :

1. cm³ mol^-1

2. litre mol^-1

3. m³ mol^-1

4. All of these 

At STP, 0.50-mole H₂ gas and 1.0 mole He gas                                  

1. have equal average kinetic energies

2. have equal molecular speeds

3. occupy equal volumes

4. have equal effusion rates

The beans are cooked in pressure cooker, because -                                   

1. Boiling point increases with increasing pressure

2. Boiling point decreases with increasing pressure

3. Extra pressure of pressure cooker softens the beans

4. Internal energy is not lost while cooking in pressure cooker

An ideal gas cannot be liquified because                                          

1. its critical temperature is always above 0$°$C

2. its molecules are relatively smaller in size

3. it solidifies before becoming a liquid

4. forces operating between its molecules are negligible