`Ice at -20^(@)C` is added to 50 g of water at `40 ^(2)C` When the temperature of the mixture reaches `0^(@) C` it is found that 20 g of ice is still unmelted .The amount of ice added to (Specific heat of water `=4.2 j//g//^(@)C`
Specific heat of Ice `=2.1 J//g //^(@)C` M
Heat of fusion of water of `0^(@)C=334 J//g)`

Options

A. 100 g
B. 40 g
C. 60 g
D. 50 g

Answer

B

Explanation

Heat lost by water `DeltaQ=msDelta T=50xx1xx40=2000 cal`
Let mass of ice=m
Heat gain by ice `DeltaQ=m xx 1/2 xx 20+(m-20)xx80=10m+80m-1600=90m-1600`
Heat gain = Heat lost
`90m-1600=2000`
m=40 gm