
The pressure
of an ideal gas is given by the expression

where
is the density of the gas.
State the meaning of the symbol
.
Use the expression to show that the mean kinetic energy
of the atoms of an ideal gas is given by the expression

Explain any symbols that you use.
Helium-4 may be assumed to behave as an ideal gas. A cylinder has a constant volume of
and contains helium-4 gas at a pressure of
and at a temperature of
. Calculate, for the helium gas,
the amount of gas,
the mean kinetic energy of the atoms,
the total internal energy.