Question

A vessel of mass 100g contains 150g of water at 30°C .How much ice is needed to cool it to 5°C.

Answer 1

Work done in lowering its temperature

H = m s dT

H = 150 (1) 25

H = 3750 calories

This energy equivalent of ice should be used to decrease the temperature.

Q = mL

3750 = m 80

m = 46.85 g