Two samples, each containing 400g of water, are mixed. The temperature of sample A before mixing was 65∘C and that of sample B was 20∘C. What will be the final temperature of the mixture? (Specific heat of water = 4186 J/(kg.K)
A
40.5∘C
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B
41.5∘C
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C
42.5∘C
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D
43.5∘C
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Solution
The correct option is C42.5∘C Given:
Mass of sample A and B, mA=mB=400g=0.4kg
Temperature of sample A, TA=65∘C
Temperature of sample B, TB=20∘C
Specific heat of water, Sw=4186J/(kg.K)
The heat lost by sample A will be equal to heat gained by sample B.
Let the temperature of the mixture be Tm.
Heat lost = Heat gained ∴mASw(TA−Tm)=mBSw(TB−T) ⇒0.4×(65−Tm)=0.4×(Tm−20) ⇒0.8Tm=34 ⇒Tm=42.5∘C