Question

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?

Answer 1

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

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...then we ignore it and focus on the ice, which has an unstated enthalpy of fusion of `"6.02 kJ/mol"`. (You should be supplying the data here...)

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

`color(blue)(|q_"removed"|) = "6.02 kJ"/cancel"mol" xx cancel"1 mol"/(18.015 cancel"g water") xx 225 cancel"g" = color(blue)"75.2 kJ"`

At constant pressure, `q = DeltaH`. What is the enthalpy change for this process in `"kJ"`?

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