How many calories must be removed from 5g of pure water at 10 °C to convert the water to ice?
A) 20
B) 80
C) 450
D) 800
E) 1200

Question

Quizplus · Accepted Answer

To convert 5g of water at 10°C to ice, we need to remove the heat of fusion, which is the amount of energy required to change a substance from a liquid to a solid state without changing its temperature. For water, the heat of fusion is 80 calories per gram. Therefore, to convert 5g of water to ice, we need to remove 5 x 80 = 400 calories. However, since we're starting at 10°C, we also need to remove the heat required to cool the water from 10°C to 0°C, which is the specific heat of water multiplied by the mass and the temperature change, or 5 x 1 x 10 = 50 calories. Therefore, the total calories that need to be removed is 400 + 50 = 450 calories (option C).

How Many Calories Must Be Removed from 5g of Pure