Answer to Question #4914 in Physical Chemistry for Khatlyn

Question

Hess's Law: When phosphorus pentachloride vapor is mixed with water vapor a reaction takes place which forms POCl3 (gas) + HCl according to this reaction: PCl5(g) + H2O(g) = POCl3 (g) + 2 HCl(g) using the follwing 4 helper equations, determine the change in enthalpy for this reaction. P + 3/2Cl2(g) + 1/2O2(g) = POCl3(g) change in enthalpy = -558.5 kJ H2(g) + Cl2(g) = 2HCl(g) change in enthalpy = -184.6 kJ PCl5(g) = P + 5/2Cl2(g) change in enthalpy = +375 kJ H2O(g) = H2(g) + 1/2O2(g) change in enthalpy = +241 kJ
a. -55 kJ
b. -89 kJ
c. -109 kJ
d. -126 kJ
e. -141 kJ