Question

The boiling point of 100 milliliters of water at sea level, vapor pressure 760 mm hg is 100oc. if, under different conditions, the boiling point of the water is 98oc, what else changed?
a.the vapor pressure decreased.
b.the vapor pressure increased.
c.the volume of water decreased.
d.the time needed to boil the water decreased.

Answer 1

It has to be D. the time needed to boil the water decreased

Answer 2

a) the vapor pressure decreased.

If 100 milliliters of water boiled at 98oC then the vapor pressure decreased. The boiling point of water changes if we vary the vapor (atmospheric) pressure. If the pressure goes down, the boiling point drops. The opposite is also true: higher pressure means a higher boiling point.