Question

Enthalpy change question??? This is what I have so far but I'm confused about the mole part of the question. P4(s) + 10 Cl2(g) = 4PCl5(s) ΔH(rxn) = -1774.0 kJ 4 PCl5(s) = 4 PCl3(l) + 4 Cl2(g) ΔH(rxn) = 495.2 kJ --------------------------------------… ----------------------------------------… -------- P4(s) + 6 Cl2(g) = 4 PCl3(l) ΔH(rxn) = [-1774.0 kJ + 495.2 kJ] = -1278.8 kJ "Use these data to calculate the enthalpy change for the formation of 3.50 mol of from phosphorus and chlorine." How do I do this?

Answer 1

P₄(s) + 10Cl₂(g) 4PCl₅(s)           ΔH = -1774.0 kJ

4PCl₅(s) 4PCl₃(l) + 4Cl₂(g)         ΔH = 495.2 kJ

P₄(s) + 6Cl₂(g) = 4PCl₃(l)                ΔH = [-1774.0 kJ + 495.2 kJ] = -1278.8 kJ

Enthalpy change for the formation of 4 moles of PCl₃ from phosphorus and chlorine = -1278.8 kJ

So, Enthalpy change for the formation of 3.50 moles of PCl₃ from phosphorus and chlorine = (-1278.8/4) 3.50 = -1118.95 kJ