Please help!?!? How do you calculate heat energy?

Question

The question I am having problems with is "Calculate the heat energy to condense 1 kg of steam at 100 degrees C and then cool the water to ice at 0 degrees C."

Answer 1

Heat energy is the sum of the heat of condensation and the heat to cool the water

Qv= heat of vaporization= mhv where

m= mass of water

hv= heat of vaporization= ~ 1000 cal/gm

Q= heat to cool the sample= mCpdT where

m= hass of water

Cp= heat capacity of water= 1 cal/gm-degC

dT= change in temperature in deg C

Qv= 1000 gm * 1000 cal/gm= 1,000,000 cal, since steam is condensed to water, the sign is negative

Qv= -1 000 000 cal

Q=mCpdT= 1000 gm * 1 cal/ gm-degC * (100-0)

Q= 1000 * 100= 100 000 cal, again the sign is negative since heat is given up

Q= - 100 000 cal

Total heat loss= - 1,100,000 cal, or 1100 kcal

Q=