Zinc is purified by distillation (evaporation followed by condensation). 

a) What is the level of vacuum (pressure) needed to distill zinc at 600 ◦C? 

b) How much energy in the form of heat (in joules per mole of zinc) is required for the distillation? Assume that the heat of condensation cannot be recovered because zinc is condensed in a separate apparatus. Data for zinc (remember conversion of atm to P a): ln p(atm) = −15250 + 1.255 ln T(K) − 21.79T(K)