Question

Using your knowledge of chemistry and the information in Reference Table H, which statement concerning propanone and water at 50°C is true?(1) Propanone has a higher vapor pressure and stronger intermolecular forces than water.(2) Propanone has a higher vapor pressure and weaker intermolecular forces than water.(3) Propanone has a lower vapor pressure and stronger intermolecular forces than water.(4) Propanone has a lower vapor pressure and weaker intermolecular forces than water.

Answer 1

The answer is (2) higher vapor pressure and weaker intermolecular forces. Propanone has a lower boiling point, so it is more volatile than water. Propanone's vapor pressure is, therefore, higher than that of water at 50 degrees Celsius. Propanone is more volatile due to the fact that the intermolecular forces that hold its molecuels together are not as strong as those that hold together molecules of water. Since the IMFs are weaker, it takes less thermal energy to break individual molecules free of each other.