A calorimeter contains 0.2 kg of water at 30°C. 0.1 kg of water at 60°C is added to it, the mixture is well stirred and the resulting temperature is found to be 35°C. The thermal capacity of the calorimeter is

Let X be the thermal capacity of calorimeter and spe­cific heat of water = 4200 J/kg-K.

Heat lost by 0.1 kg of water = Heat gained by water in calorimeter + Heat gained by calorimeter

0.1 × 4200 × (60 - 35) = 0.2 × 4200 × (35 - 30) + X(35 - 30) 

                        10500 = 4200 + 5X $\Rightarrow$ X = 1260 J/K