Final answer:
The enthalpy of the reaction 2 M(s) + 3 Cl2(g) → 2MCl3(s) is found by using Hess's law to rearrange and sum the enthalpies of given reactions, ensuring stoichiometric coefficients align with the desired reaction.
Step-by-step explanation:
To determine the enthalpy of the reaction 2 M(s) + 3 Cl2(g) → 2MCl3(s), we must use Hess's law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes for individual steps that lead to the overall reaction.
The given reactions are:
- M(s) + 6 HCl(aq) → MCl3(aq) + 3 H2(g), ΔH = -811.0 kJ
- HCl(g) → HCl(aq), ΔH = -74.8 kJ
- H2(g) + Cl2(g) → 2 HCl(g), ΔH = -1845.0 kJ
- MCl3(solid) → MCl3(aqueous), ΔH = -445.0kJ
First, we need to adjust the reactions to match the desired reaction. This might involve reversing and multiplying through by appropriate stoichiometric coefficients. Then we add the enthalpies for each step, taking into account the changes made.