(25 points) Below is a graph of the activities of silver, Ag, and lead, Pb, over liquid solutions at1000°C as a function of the mole fraction Pb in the liquid.

The vapor pressures over pure liquid silver and over pure liquid lead are p,= 198 Pa and påg = 0.789 Pa, respectively. a) What would be the total vapor pressure over a 42:58 Pb:Ag liquid solution. b) What would be the Gibbs energy of mixing of 0.42 mole of Pb and 0.58 moleof Ag to form a liquid solution at1000°C? c) How does this differ from the Gibbs energy of mixing of an ideal solution and what is thereason for the difference? d) Estimate Henry's Law constant for Pb, assuming pure liquid Pb as the standard state.