Ice at 0°C is added to 200gms of water initially at 70°C in a vacuum flask. When 50gms of ice has been added and has all melted the temperature of the flask and the contents become 40°C. When 80gms of ice has been added and has all melted the temperature becomes 10°C. Neglecting heat loss to the surroundings calculate latent heat of fusion of ice

1 answer

the water in the flask loses heat to the ice
... (mass of water) * (specific heat of water) * (temperature change)

the ice melts , and the resulting water is heated to the final flask temperature
... (mass of ice) * (latent heat of fusion of ice)
... plus ... (mass of water) * (specific heat of water) * (temperature change)