Example Question #1 : Enthalpy
Suppose that 1.5 moles of potassium reacts completely with an excess of chlorine gas. What is the enthalpy change of the reaction?
First, note that heat is a product of the reaction. This means that the reaction releases heat and is exothermic, so the enthalpy change must be negative. Next, consider that 2 moles of sodium would react to produce 640 kJ. Thus, 1.5 moles of sodium would react to produce
Hence, the enthalpy change is .