Answer
238.2 torr
Work Step by Step
The vapor pressure of a solution with two components is:
P(total) = mole fraction A * VP pure a + mole fraction B * VP pure b
We are told the VP of pure water is 175 torr and that of ethanol is 400 torr. Since the mole fraction of ethanol is 0.281 then the mole fraction of water is 1-0.281 = 0.719. Therefore, we have:
P = 0.719 * 175 torr + 0.281*400 torr = 238.2 torr