This experiment explores Hess’ Law, a cornerstone of thermochemistry. The enthalpy of reaction ∆H for two acid-base reactions serves as key property to employ and confirm Hess’ law.
The two acid-base reactions utilize a strong acid – HCl – as well as a weak acid – CH3COOH. The base used is solid sodium hydroxide.
1. The heat of neutralization of solid sodium hydroxide with an aqueous solution of an acid might be determined directly in a one-step reaction or indirectly using a two-step reaction. Explain the difference between a one-step and a two-step reaction mechanism when determining the heat of neutralization.
2. Would you expect different values for the heat of the neutralization reaction, when solid NaOH is neutralized with an aqueous solution of a weak acid or with an aqueous solution of a strong acid? Explain your answer.
3. Explain how the fact that the weak acid is only partially dissociated might cause discrepancies between a theoretical predicted and an experimentally determined value.