During the phase transition vapour --> liquid water, the temperature of the water does not change; the molecules of water release heat and the amounf of heat released is equal to
[tex]Q=mL_e[/tex]
where
m is the mass of the water
[tex]L_e[/tex] is the latent heat of evaporation.
For water, the latent heat of evaporation is [tex]L=2257 kJ/kg[/tex], while the mass of the water is
[tex]m=1234 g=1.234 kg[/tex]
so, the amount of heat released in the process is
[tex]Q=mL_e = (1.234 kg)(2257 kJ/kg)=2785 kJ[/tex]
