Question

How many kilocalories are released when 12.0 g of H2O(g) is condensed?

Answer 1

For the evaporation of water, H2O(l)→H2O(g), at 100 ∘C, ΔH = +9.72 kcal/mol (+40.7 kJ/mol).

condensed is reverse of the above process

so

H2O(g)→H2O(l), at 100 ∘C, ΔH = -9.72 kcal/mol (-40.7 kJ/mol).

for 1mole of H2O ....................... -9.72 K.cal

(12/18) moles of water .........................?

      = (12/18)*(-9.72) = -6.48 K.cal

6.48 kilocalories are released when 12.0 g of H2O(g) is condensed