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Question
A mass of 200 g of mercury at 100°C is poured into water at 20°C. If the final temperature of the mixture is 25°C, find the mass of water. (Sp. heat cap. of mercury is 140 J/kgK).
Solution
Let the mass of water be m.
Heat lost by mercury = Heat gained by water
0.2 x 140 x (100 - 25) = m x 4200 x (25 - 20)
or, m = `(0.2 xx 140 xx 75)/(4200 xx 5)` = 0.1 kg = 100 g
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