The heat released during combustion in an excess of oxygen 1 ton of coal with a mass fraction of carbon 84% was …

Given:
m (coal) = 1 t = 1,000,000 g
ω (C) = 84%

To find:
Q -?

Decision:
1) Write the reaction equation:
C + O2 => CO2 + 395 kJ;
2) Calculate the mass of carbon:
m (C) = ω (C) * m (coal) / 100% = 84% * 1,000,000 / 100% = 840,000 g;
3) Calculate the amount of carbon substance:
n (C) = m (C) / M (C) = 840,000 / 12 = 70,000 mol;
4) Calculate the amount of heat released:
1 mol C – 395 kJ;
70,000 mol C – Q kJ;
Q = 70,000 * 395/1 = 27,650,000 kJ = 27.65 GJ.

Answer: The amount of heat released is 27.65 GJ.