(a) Use the equation of state for an ideal gas and the definition of the average coefficient of volume expansion, in the form $\beta=(1 / V) d V / d T$, to show that the average coefficient of volume expansion for an ideal gas at constant pressure is given by $\beta=1 / T$, where $T$ is the absolute temperature. (b) What value does this expression predict for $\beta$ at $0^{\circ} \mathrm{C}$ ? Compare this with the experimental values for helium and air in Table $19.2 .$