A solution consists of 10 g of liquid x, whose molecular weight is 50, and 9g of liquid y, whose molecular weight is 30. the vapor pressure of pure x and pure y at 20 C are 40 and 70mm, respectively. calculate the mole fractions of x and y in the solution. if the solution is ideal, what is the partial pressure of x over the solution at 20 C? to what value would you reduce the external pressure on the system in order to initiate boiling at 20 C?