CBSE Class 12-science Answered

Molar mass of methanol = 32 g mol^-1

Molar mass of ethanol = 46 g mol^-1

n_methanol = 40 / 32 = 1.25 moles

n_ethanol = 60 / 46 = 1.30 moles

n _total = 1.25 + 1.30 = 2.55 moles

X _methanol = 1.25 / 2.55 = 0.49

X _ethanol = 1.30 / 2.55 = 0.51

p_total = p^o_ethanol + (p^o_methanol  - p^o_ethanol)  x  X_methanol

           = 44.5 + (88.7 – 44.5) x 0.49

           = 66.16 mm Hg

Mole fraction in vapour phase,

p_methanol = 0.49 x 66.16 = 32.64 mm Hg

p_ethanol = 0.51 x 66.158 = 33.74 mm Hg

y_methanol = 32.64 / 66.16 = 0.49

y_ethanol = 33.74 / 66.16 = 0.51