Question

how many moles of liquid water must freeze to remove 100 kJ of heat?

Answer 1

Heat removed removed by liquid water to freeze = mLf

Where :

m is the mass of liquid water and Lf the latent fusion of ice.

Latent fusion of ice = 334 joules per gram.

Heat removed = 100000 joules

100000 joules = m × 334joules / gram

m = 100000/334 = 299.40 g

Molar mass of water ( H₂O) : 1 × 2 moles of hydrogen + 16 × 1 mole of oxygen = 18g

Moles = mass / molar mass

299.40 / 18 = 16.63 moles.

We therefore need 16.63 moles of liquid water.