How much calories of heat is given off?

Question

It is given that substance whose water equivalent is 50 grams , loses its temperature from 50°C to 30°C . How much calories of heat is given off

Answer 1

Firstly, water equivalent (\(w\)) is the weight of water required to transfer the same amount of heat as transferred by given weight of substance (\(w_o\)). So, \(w = \frac{w_o s_o}{s_w}\).

Secondly, \(\Delta Q = w_o s_o\Delta T = ws_w\Delta T = 50 \ g \times 1 \ calg^{-1}K^{-1} \times -20 \ K = -1 \ kcal\)

Hence, 1 kcal of heat is released.