How much coal must be burned to obtain 68 kJ of heat?

univerkov | January 29, 2021 | education

Initial data: Q (received amount of thermal energy) = 68 kJ or 68 * 10 ^ 3 J.

Reference data: q1 (specific heat of combustion of coal) = 2.7 * 10 ^ 7 J / kg; q2 (specific heat of combustion of charcoal) = 3.4 * 10 ^ 7 J / kg.

1) Combustion of coal: m1 = Q / q1 = 68 * 10 ^ 3 / (2.7 * 10 ^ 7) = 2.51 * 10 ^ -3 kg = 2.52 g.

2) Burning charcoal: m2 = Q / q2 = 68 * 10 ^ 3 / (3.4 * 10 ^ 7) = 2 * 10 ^ -3 kg = 2 g.

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