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For the irreversible reaction, Ca+ 2C = Ca C2 , Δ H°298 = - 60000 J . mole-1 . If a system initially containing 2 moles of calcium, 3 moles of carbon and 1 mole of calcium carbide is allowed to react to completion, the heat evolved at 298 K will be
30,000 J
60,000 J
90,000 J
2,40,000 J