The amount of heat needed to melt 2kg of ice at its melting point, when latent heat of ice is 80cal/g, is _____. (1cal=4.184J)
A
40×105J
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B
6.7×105J
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C
3.35×105J
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D
1.675×105J
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Solution
The correct option is B6.7×105J Latent heat of ice is defined as the amount of heat needed to convert 1g of ice into water. As given in the question, its value is 80cal/g.
Since 1cal=4.184J 80cal/g=80×4.184J/g =334.72J/g
Heat needed to melt 2kg of ice is:
Heat = mass × latent heat of ice =2×334.72kJ =669.44kJ =669.44×103J=6.7×105J