The efficiency of the spirit lamp is 10%. How much alcohol needs to be burned in an alcohol lamp

Initial data: η (alcohol lamp efficiency) = 10% = 0.1; m1 (ice mass) = 1 kg; t0 (initial ice temperature) = 0 ºС.

Reference data: q (specific heat of combustion of alcohol) = 2.7 * 10 ^ 7 J / kg; λ (specific heat of melting of ice) = 3.4 * 10 ^ 5 J / kg.

The required mass of alcohol is determined from the formula: η = Q1 / Q2 = λ * m1 / (q * m2), whence m2 = λ * m1 / (η * q).

Let’s calculate: m2 = 3.4 * 10 ^ 5 * 1 / (0.1 * 2.7 * 10 ^ 7) = 0.126 kg or 126 g.

Answer: 126 grams of alcohol must be burned in an alcohol lamp.