CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
A cylinder fitted with a frictionless, massless piston contains 0.500mol of helium gas at 298K. The external pressure is suddenly increased to a constant value of 2500atm, and the system is allowed to reach mechanical equilibrium at the same temperature.
Helium is assumed to remain in a single gaseous phase throughout the process.
(a) Calculate the volume that the gas would occupy at 2500atm if it behaved ideally.
(b) Experimental measurement shows that the equilibrium volume is 0.280L. Compute the compressibility factor Z for helium under these conditions.
(c) Based on the sign and magnitude of the deviation you calculated in part (b), determine which non-ideality (intermolecular attractions or finite molecular volume) is primarily responsible for the observed behavior of helium at 2500atm. Justify your answer with reference to helium’s molecular characteristics.