The numerical value of $\frac{\mathrm{N}}{\mathrm{n}}$ (where, N is the number of molecules in a given sample of gas and n is the number of moles of the gas) is :

• 8.314

• 6.02 × 10²³

• 0.0821

• 1.66 × 10^-19

The mass of 11.2 L of ammonia gas at STP is:

• 8.5 g

• 85 g

• 17 g

• 1.7 g

The enthalpy of a monoatomic gas at T Kelvin is :

• $\frac{7}{2}$RT

• $\frac{5}{2}$RT

• $\frac{1}{2}$RT

• $\frac{1}{2}$

The enthalpy change for the transition of liquid water to steam is 40.8 kJ mol^-1 at 373 K. What is the entropy of vaporisation of water ?

• 209.4

• 109.4

• -109.4

• -209.4

If the absolute temperature of a gas is doubled and the pressure is reduced to one half, the volume of the gas will :

• remain unchanged

• be doubled

• increase four fold

• be halved

To what temperature must a neon gas sample be heated to double its pressure, if the initial volume of gas at 75°C is decreased by 15.0%?

• 319°C

• 592°C

• 128°C

• 60°C

The van der Waals' equation for a real gas is given by the formula $\left[\mathrm{P} + \frac{{\mathrm{n}}^2\mathrm{a}}{{\mathrm{V}}^2}\right]$ (V - nb) = nRT where, P, V, T and n are the pressure, volume, temperature and the number of moles of the gas. Which one is the correct interpretation for the parameter a?

• The parameter a accounts for the finite size of the molecule, not included temperature in the ideal gas law

• The parameter a accounts for the shape of gas phase molecules

• The parameter a accounts for intermolecular interaction's present in the molecule

• The parameter a has no physical significance and van der Waals' introduced it as a numerical correction factor only

When the product of pressure and volume is plotted against pressure for a given amount of gas, the line obtained is :

• parallel to X-axis

• parallel to Y-axis

• linear with positive slope

• linear with negative slope

259.

Air at sea level is dense. This is a practical implimentation of :

• Boyle's law

• Charles' law

• Avogadro's law

• Dalton's law

The r.m.s. velocity of CO₂ at a temperature T (in kelvin) is x cm s^-1. At what temperature (in kelvin), the r.m.s. velocity of nitrous oxide would be 4x cm s^-1? (Atomic weights of C, N and O are respectively 12, 14 and 16)

• 16 T

• 2 T

• 4 T

• 32 T