Latent Heat Numericals

In this post, we will solve numerical problems based on latent heat concepts. [practice problems & extra problems].

Latent Heat Numericals – solved

Question] Calculate the amount of heat necessary to change 0.20 kg of ice at 0^oC into the water at 10^oC.

Solution thoughts:
A phase change occurs in the process, latent heat is first used in melting the ice and then specific heat in raising the temperature of the water. The solution then requires finding the heat for each phase.

Solution steps:
The total heat necessary is found in two steps: ice melting at 0^oC and water warming from 0^oC to 10^oC.
H = H_{melt ice} + H_{change T}
= mL_f + m c dT
= (0.20 kg)(80 kcal/kg) + (0.20 kg)(1.00 kcal/kg^oC)(10^oC – 0^oC)
= 18 kcal

Latent Heat Practice Problem:

Question] How much heat must be removed from 0.20 kg of water at 108C to form ice at 08C?