Calculate the liquid and vapor compositions of a binary mixture of isobutane (1) and hydrogen sulfide (2) at 4.5"c and 8.77 bar. the excess gibbs energy can be described by the three-suffix margules equation (truncating the redlich-kister expansion after the second term) with these parameters: a = 1918 [j/mol] and b = -1074 [j/mol]

(a) assume the vapor can be treated as an ideal gas. (b) correct for the vapor-phase nonideality using the lewis fugacity rule.