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).

Answer 1

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