How many grams of kerosene do you need to burn to bring 4 kg of water to a boil and evaporate 500 g

How many grams of kerosene do you need to burn to bring 4 kg of water to a boil and evaporate 500 g of it if the initial water temperature is 20C? Heater efficiency 25%.

Given: m2 is the mass of vapor. water (m2 = 0.5 kg); L – heat of steam. (L = 2.3 * 10 ^ 6 J / kg); Cw – heat capacity (Cw = 4200 J / (kg * K)); m1 – total mass (m1 = 4 kg); tboil – temp. boiling (tboil = 100 ºС); t0 – early. pace. (t0 = 20 ºС); η – efficiency (η = 0.25); qk is the heat of combustion of kerosene (qk = 4.6 * 10 ^ 7 J / kg).

Formula: η = m2 * L + Cw * m1 * (tboil – t0)) / (qk * mk) and mk = m2 * L + Cw * m1 * (tboil – t0)) / (η * qk).

Calculation: mk = 0.5 * 2.3 * 10 ^ 6 + 4200 * 4 * (100 – 20)) / (0.25 * 4.6 * 10 ^ 7) = 0.217 kg.