Heat and Thermodynamics 1 Question 14

14. 2kg of ice at 20C is mixed with 5kg of water at 20C in an insulating vessel having a negligible heat capacity. Calculate the final mass of water remaining in the container. It is given that the specific heats of water and ice are 1kcal/kg/C and 0.5kcal/kg/C while the latent heat of fusion of ice is 80kcal/kg

(2003, 2M)

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Solution:

  1. Heat released by 5kg of water when its temperature falls from 20C to 0C is,

Q1=mcΔθ=(5)(103)(200)=105cal

when 2kg ice at 20C comes to a temperature of 0C, it takes an energy

Q2=mcΔθ=(2)(500)(20)=0.2×105cal

The remaining heat Q=Q1Q2=0.8×105 cal will melt a mass m of the ice, where,

m=QL=0.8×10580×103=1kg

So, the temperature of the mixture will be 0C, mass of water in it is 5+1=6kg and mass of ice is 21=1kg.



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