A piece of ice (heat capacity `=2100 J kg^(-1) .^(@)C^(-1)` and latent heat `=3.36xx10^(5) J kg^(-1)`) of mass m grams is at `-5 .^(@)C` at atmospheric pressure. It is given 420 J of heat so that the ice starts melting. Finally when the ice . Water mixture is in equilibrium, it is found that 1 gm of ice has melted. Assuming there is no other heat exchange in the process, the value of m in gram is

Options

A. 4
B. 8
C. 2
D. 5

Answer

B

Explanation

Heat supplied = Heat used in converting m grams of ice from `-5^(@)C` to `0^(@)C+` Heat used in converting 1 gram of ice at `0^(@)C` to water at `0^(@)C`
`rArr 420=m xx (2100)/(1000)xx5+(1xx3.36xx10^(5))/(1000)`
`rArr 420=m xx 10.5+336 " " therefore m=(84)/(10.5)=8` grams