How much charcoal you need to burn to evaporate 10 kg of water with an initial temperature of -20 ° t.

Data: m (mass of water) = 10 kg; t0 (initial water temperature) = -20 ºС; q (heat of combustion of charcoal) = 34 * 10 ^ 6 J / kg; C1 (heat capacity of ice) = 2100 J / (kg * K); λ (heat of melting of ice) = 3.4 * 10 ^ 5 J / kg; C2 (heat capacity of water) = 4200 J / (kg * K); L (water vaporization) = 2.3 * 10 ^ 6 J / kg.

m * (C1 * (0 – t0) + λ + C2 * (100 – 0) + L) = q * m3.

m3 = m * (C1 * (0 – t0) + λ + C2 * (100 – 0) + L) / q = 10 * (2100 * 20 + 3.4 * 10 ^ 5 + 4200 * 100 + 2.3 * 10 ^ 6) / (34 * 10 ^ 6) = 0.912 kg or 912 g.