Sol. In such mixing problems, it is advisable to first convert all the phases of mixing substance

into a Single phase at a common temperature and keep the excess or required heat for this aside and finally supply or extract that amount of heat to get the final equilibrium temperature of mixture. As in this problem 0.5 kg of ice is given at . To convert it into water at if we require amount of heat, the we have

(- ve sign for heat required)
The 2 kg of water is available at . To convert it into , it releases some heat, say . Then we have

Thus we have the final mixture as

Thus finally we can supply the availabe heat of the 2.5 kg water at to get find temperature of mixure as

Thus final result is of 2.5 kg water after mixing.