ICSE Class 10 Physics 2017 Solved Paper

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Question : 34 of 65
 
Marks: +1, -0
Calculate the mass of ice needed to cool 150g of water contained in a calorimeter of mass 50g at 32∘C such that the final temperature is 5∘C.
Specific heat capacity of calorimeter =0.4J∕ gCC
Specific heat capacity of water =4.2J∕g∘C
Latent heat capacity of ice =330J∕g
Solution:
Let the mass of ice be =′m′g .
As ice will gain heat from calorimeter and water, it will undergo conversion as :
Ice → Water → Water
(at 0∘C ) (at 0∘C ) (at 5∘C )
So, heat gained =mL+mc∆T
=m×330+m×4.2×(5−0)
=330m+21m
=(351m)J.
∵ Heat is lost by calorimeter and water both,
∴ Heat lost by calorimeter
=m1c1∆T1
=50×0.4×(32−5)
=540J
Heat lost by hot water
=m2CW∆T2
=150×4.2×(32−5)
=150×4.2×27
=17010J
∴ Total heat lost =540+17010=17550J
By the principle of calorimetry
Heat gained = Heat lost
∴351m=17550
or m=17550351=50g
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