Question

The heat of vaporization of water is `2260` `Jg^-1`. How do you calculate the molar heat of vaporization `(Jmol^-1)` of water?

Answer 1

The key thing needed is to know the molar mass of water: `18` `gmol^-1`. If each gram of water takes `2260` `J` to vaporise it, and a mole is `18` `g`, then each mole takes `18xx2260 = 40,680` `Jmol^-1` or `40.68` `kJmol^-1`.