Assume that heat capacity of `H_(2) O` to be `4.2 xx 10^(3) J kg ^ (-1) K^(-1)` and the latent heat of vapourisation of `H_(2) O` to be `22.5 xx 10^(5) J kg^(-1)`. The amount of heat in joule required to heat 1 kg of water from `50^(@)C` to `100^(@)C` and then to convert into steam at `100^(@)C` is

Options

A. `12.3 xx 10^(5) J`
B. `24.6 xx 10^(5) J`
C. `20.0 xx 10^(5) J`
D. `18.6 xx 10^(5) J`

Answer

B

Explanation

Total heat = heat required to raise the temperature of water + Heat reqired to convert water into steam
`Q = m_(1)L + m_(2)sDeltat`
` = (1 xx 22.5 xx 10^(5)) + [4.2 xx 10^(3) xx (100 - 50)]`
` = 24.6 xx 10^(4) J`
` = 24.6 xx 10^(5) J`