What mass of water can be heated from 15 * C to boiling if 250 g of natural gas is burned?

Initial data: t0 (initial water temperature) = 15 ºС; m2 (mass of natural gas) = 250 g = 0.25 kg.

Reference values: tboil. (boiling point of water) = 100 ºС; C (specific heat capacity of water) = 4200 J / (kg * K); q (beats heat of combustion of natural gas) = 34 MJ / kg = 34 * 10 ^ 6 J / kg.

All the heat from the combustion of natural gas will go to heating water and the equality is true: C * m1 * (tboil – t0) = q * m2, whence m1 = q * m2 / (C * (tboil – t0)).

Let’s calculate: m1 = 34 * 10 ^ 6 * 0.25 / (4200 * (100 – 15)) = 23.8 kg.