Steam at `100^@C` is passed into 1.1 kg of water contained in a calorimeter of water equivalent 0.02 kg at `15^@C`till the temperature of the calorimeter and its contents rises to `80^@C` . The mass of the steam condensed in kilogram is

Options

A. `0.130`
B. `0.065`
C. `0.260`
D. `0.135`

Answer

A

Explanation

Heat is lost by steam in two stages (i) for charge of state from steam at `100^(@)C` to water at `100^(@)C` is `mxx540` (ii) to change water at `100^(@)C` to water at `80^(@)C` is `m xx 1 xx (100-80)`, where `m` is the mass of steam condensed.
Total heat lost by steam = `m xx 540+mxx20=560m cal`
Heat gained by calorimeter and its contents
`=(1.1 + 0.2) xx (80-15) = 1.12 xx 65 cal`
Using principle of calorimetry,
Heat gained = heat lost
`:. 560 m = 1.12 xx 65`
`m = 0.130 gm`.