How much heat must be removed to freeze a tray of ice cubes at 0 C if the water has a mass of 225 g?

Well, if the tray itself has a negligible heat capacity...

Hence, the amount of heat that is released at constant pressure is:

HINT: read the question wording again. Which direction is the heat flowing, and is the ice the system or surroundings?

The amount of heat $q$ required to freeze a substance can be calculated using the equation:

$q = m \cdot \Delta H_f$

Where:

• $q$ is the heat absorbed or released (in joules)
• $m$ is the mass of the substance (in grams)
• $\Delta H_f$ is the heat of fusion (in joules per gram)

For water, the heat of fusion is $334 \, \text{J/g}$.

Given that the mass of water is $225 \, \text{g}$, and assuming the temperature change is from $0^\circ \text{C}$ to $0^\circ \text{C}$ during freezing, the heat required is:

$q = 225 \, \text{g} \times 334 \, \text{J/g} = 75150 \, \text{J}$

So, $75150 \, \text{J}$ of heat must be removed to freeze the tray of ice cubes.