Answer:
The value of ΔHf that was found using Spartan was -51.59962 kJ/mol. The experimental value found for ΔHvap was 44.1 kJ/mol. They are close in magnitude, but their signs are different. This is because ΔHf is the enthalpy change when one mole of a substance is formed from its elements in the standard state and under the same conditions. Because ΔHf is the enthalpy change, it can be either negative or positive. In this case, when it is negative, it signifies that the reaction is exothermic. ΔHvap is the amount of energy necessary to vaporize one mole of a substance from its liquid state to its gas state. Therefore, unlike ΔHf, it is always positive because energy is required to vaporize a substance, thus making it a constant endothermic reaction.