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

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

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 compressibility factor for H₂ and He is usually:

1. >1                                     

2. =1

3. <1                                     

4. either of these

Boyle's law is applicable in :

1. Isobaric process

2. Isochoric process

3. Isothermal process

4. Adiabatic process

The correct value of the gas constant 'R' is close to 

1. 0.082 L atm K

2. 0.082 L atm K^-1 mol^-1

3. 0.082 L atm^-1 K mol^-1

4. 0.082 L^-1 atm^-1 K mol

The number of molecules present in 1 mL of gas or vapor at STP is:

1. called Loschmidt's number

2. equal to 2.617 x 10¹⁹ per mL

3. both (1) and (2)

4. none of the above

600 cc of a gas at a pressure of 750 mm is compressed to 500 cc. Taking the temperature to remain constant, the increase in pressure is:                                         

1. 150 mm                       

2. 250 mm

3. 350 mm                      

4. 450 mm

An ideal gas expands according to PV=constant. On expansion, the temperature of the gas:

1. Will rise.

2. Will drop.

3. Will remain constant.

4. Cannot be determined because the external pressure is not known.