Question

4kg of hot water at 343 k is added to 6kg of water at 293k.The resultant temp. is 313 k. calculate the heat lost by the hot water and heat gained by the cold water assuming that there is no heat loss to the surroundings.

Answer 1

1. 4 kg of hot water:
(i) We have : Q = mc.
(ii) = (2 - 1) = (313 - 343) = -30 K

The negative sign indicates that, heat energy is given out

(iii) Substituting the known values we get: Q = 44200-30 = -504000 J
2. 6 kg of water:
(i) We have : Q = mc.
(ii) = (2 - 1) = (313 - 293) = 20 K
(iii) Substituting the known values we get: Q = 6420020 = 504000 J

3. So we can write:
Heat energy lost by the hot water = heat energy gained by the cold water