General Questions These questions are not explicitly keyed to chapter topics; many requ...

General Questions

These questions are not explicitly keyed to chapter topics; many require integration of several concepts.

Mercury is a poison, and its vapor is readily absorbed through the lungs. Therefore it is important that the partial pressure of mercury be kept as low as possible in any area where people could be exposed to it (such as a dentist’s office). The relevant equilibrium reaction is

For Hg(g), ΔHf ° = 61.4 kJ/mol, S° = 175.0 J K^-1 mol^-1, and ΔGf° = 31.8 kJ/mol. Use data from Appendix J and these values to evaluate the vapor pressure of mercury at different temperatures. (Remember that concentrations of pure liquids and solids do not appear in the equilibrium constant expression, and for gases K° involves pressures in bars.)

(a) Calculate ΔG° for vaporization of mercury at 25 °C.

(b) Write the equilibrium constant expression for vaporization of mercury.

(c) Calculate K° for this reaction at 25 °C.

(d) What is the vapor pressure of mercury at 25 °C?

(e) Estimate the temperature at which the vapor pressure of mercury reaches 10 mm Hg.