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__________________?

Question

Accepted Answer

90,000 J. The reaction is Ca + 2C -> CaC2. Initial moles are 2 Ca, 3 C, 1 CaC2. Carbon is the limiting reactant (requires 4 moles for 2 Ca, but only 3 available). Moles of Ca reacting = 3/2 = 1.5 mol. Heat evolved = 1.5 * 60,000 J = 90,000 J.