If we work it out with direct proportions, the vapor pressure of propanone is 56 degrees Celsius. The atmospheric pressure is about 101 kPa. If the vapor pressure is equal to the atmospheric pressure, the substance boils. Therefore, if we hold a linear proportion, 45/56 = x/101. 56x = 101*45, x = 101*45/56 = 81. The closest choice here is (3) 70 kPa.
Next time, please provide us with Reference Table H.
