How much heat must be absorbed by ice of mass m = 1000 g at -10 ˚C to take it to liquid state at 15 ˚C? cice = 2220 Jkg−1K−1 cliq = 4190 Jkg−1K−1 LF=333kJkg−1
A
418 kJ
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B
300 kJ
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C
318 kJ
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D
400 kJ
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Solution
The correct option is A 418 kJ Heating process is accomplished in three steps:
Step 1: Sensible heat absorbed to raise temperature of ice from -10 ˚C to 0 ˚C: Q1 = cicem(Tf–Ti) = (2220 Jkg−1K−1 ) (1 kg) [0 ˚C - (- 10 ˚C) ] = 22200 J = 22.2 kJ
Step 2: Latent heat absorbed for phase change from ice to water at 0 ˚C: Q2 = LFm = (333 kJkg−1 ) (1 kg) = 333kJ
Step 3: Sensible heat absorbed to raise temperature of water from 0 ˚C to 15 ˚C: Q3 = cliqm(Tf–Ti) = (4190 Jkg−1K−1 ) (1 kg) (15 ˚C – 0 ˚C) =62850 J = 62.85 kJ Total heat absorbed = Q1+Q2+Q3 =(22.2+333+62.85)kJ =418.05kJ=418kJ