For this question, take the specific heat of liquid water to be 4190 J/kg⋅K, the specific heat of ice to be 2100 J/kg⋅K, and the heat of fusion for water to be 3.34×105 J/kg.
An insulated beaker with negligible mass contains liquid water with a mass of 0.335 kg and a temperature of 69.1oC .
How much ice at a temperature of -18.3oC must be dropped into the water so that the final temperature of the system will be 29.0oC?