[cabaal]

A mixture of water and nitrobenzene distills at 99.3 C when the barometric pressure is 760 mm Hg. The vapor pressure of water at 99.3 C is 740 mm Hg. Calculate the weight ratio of water to nitrobenzene that will distill.

I really have no idea how to do this. Are these vapor pressures the same as partial pressures?

[cabaal]

(760 - 740) mm Hg = 20 mm Hg = partial pressure of the nitrobenzene
(20 mm Hg / 740 mm Hg) = 0.027 mol ratio * (123 g/mol nitrobenzene / 18 g/mol water) = 0.1845 weight ratio of nitrobenzene/water

Would this be correct?

[Borek]

Looks reasonable at first glance. Second opinion won't hurt.

[rabolisk]

Looks right to me. Can't see how you would solve it any other way.

[cabaal]

Thanks.