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 if found to be `35^@C`. The thermal capacity of the calorimeter is

Options

A. `6300 J//K`
B. `1260 J//K`
C. `4200 J//K`
D. none of these

Answer

B

Explanation

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
`implies0.1xx4200xx(60-35)`
`=0.2xx4200xx(35-30)+X(35-30)`
`10500=4200+5 X implies X=1260 J//K`