States of matter: Practice Questions

Which of the following substances forms a giant molecular (macromolecular) lattice in the solid state?

A sample of an unknown gas has a mass of \(0.441\text{ g}\)\). It occupies a volume of \(240\text{ cm}^3\) at a pressure of \(101\text{ kPa}\) and a temperature of \(27^{\circ}\text{C}\).
What is the relative molecular mass, \(M_r\), of the gas?
[\(R = 8.31\text{ J K}^{-1}\text{ mol}^{-1}\)]

Why does the volume of a fixed mass of an ideal gas increase when the temperature is increased at constant pressure?

Which substance exists as a giant molecular (macromolecular) lattice in its solid state?

Under which set of conditions does a real gas deviate most from ideal behavior?

(a) State two assumptions of the kinetic theory as applied to an ideal gas.
(b) Explain the origin of the pressure exerted by a gas on the walls of its container in terms of the collisions and movement of gas molecules.

A student uses a gas syringe method to determine the relative molecular mass of a volatile organic liquid. A \( 0.148 \text{ g} \) sample of the liquid is injected into a syringe and heated. At a temperature of \( 373 \text{ K} \) and a pressure of \( 100 \text{ kPa} \), the liquid evaporates to produce \( 62.0 \text{ cm}^3 \) of gas. [The gas constant, \( R = 8.31 \text{ J K}^{-1} \text{ mol}^{-1} \)]
(a) Calculate the number of moles of gas produced, ensuring all units are converted to SI units.
(b) Calculate the relative molecular mass, \( M_r \), of the organic liquid.
(c) Suggest the effect on the calculated \( M_r \) value if the liquid did not evaporate completely. Justify your answer.
(d) Explain why real gases deviate from ideal behavior at very high pressures.