Vaporizing 5.00g of H2O(l) requires 12.2 kj. What is the molar heat of vaporization of water when water's specific heat is 4.184 J/g degrees C

Answer 1

How many moles of water are there?

5.00 g H2O x 1 mole H2O / 18 g = 0.278 moles H2O

How many joules of heat energy were used to vaporize this amount of H2O?

12.2 kJ

What is the molar heat of vaporization?

12.2 kJ / 0.278 moles = 43.9 kJ / mole

(Note: the specific heat of water does not enter into these calculations)