1. When a liquid and its vapour are in equilibrium and the pressure is suddenly decreased, cooling occurs. (JEE 1984)
True
Reason: The decrease in pressure results in further evaporation of the liquid into gaseous phase. The energy required for this is realized from the liquid itself which causes a decrease in temperature.
2. Kinetic energy of molecules is zero at 0°C. (JEE 1985)
Ans: False
The equation relating energy of molecules to temperature is in absolute temperature and not centigrade temperature.
3. A gas in a closed container will exert much higher pressure due to gravity at the bottom than at the top. (JEE 1985)
False.
It is equal in all directions.
4. Heat capacity of a diatomic gas is higher than that of a monatomic gas. (JEE 1985)
True
Diatomic gas has translational, rotational, and vibrational energies. Monatomic gas has only translational energy.
5. In the van der Waals equation,
[p + n²a/V²][V-nb] = nRT
the constant ‘a’ reflects the actual volume of the gas molecules.
False
Reason: In the equation ‘a’ is a measure of the forces of attraction between gaseous molecules and b is a measure of effective volume occupied the molecules of 1 mol of a gas.
True
Reason: The decrease in pressure results in further evaporation of the liquid into gaseous phase. The energy required for this is realized from the liquid itself which causes a decrease in temperature.
2. Kinetic energy of molecules is zero at 0°C. (JEE 1985)
Ans: False
The equation relating energy of molecules to temperature is in absolute temperature and not centigrade temperature.
3. A gas in a closed container will exert much higher pressure due to gravity at the bottom than at the top. (JEE 1985)
False.
It is equal in all directions.
4. Heat capacity of a diatomic gas is higher than that of a monatomic gas. (JEE 1985)
True
Diatomic gas has translational, rotational, and vibrational energies. Monatomic gas has only translational energy.
5. In the van der Waals equation,
[p + n²a/V²][V-nb] = nRT
the constant ‘a’ reflects the actual volume of the gas molecules.
False
Reason: In the equation ‘a’ is a measure of the forces of attraction between gaseous molecules and b is a measure of effective volume occupied the molecules of 1 mol of a gas.