To find the desired mass of burnt charcoal, we apply the formula: Q = qdu * m, whence we express: m = Q / qdu.
Values of variables and constants: Q – required heat energy (Q = 6.8 * 10 ^ 7 J); qд – specific heat of combustion of charcoal (qд = 3.4 * 10 ^ 7 J / kg).
Let’s make a calculation: m = Q / qdu = 6.8 * 10 ^ 7 / (3.4 * 10 ^ 7) = 2 kg.
Answer: It will be necessary to burn 2 kg of charcoal.
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