Calculate ΔS°_rxn (J/K) for the formation reaction of the salt MgO (s).

• A. −217.4 J/K
• B. −108.7 J/K
• C. +27.0 J/K
• D. +162.6 J/K
• E. +265.6 J/K

Answer: (B)

Verified step by step guidance

1. Identify the chemical reaction for the formation of MgO(s). The formation reaction typically involves the elements in their standard states: Mg(s) + 1/2 O2(g) -> MgO(s).
2. Determine the standard entropy values (S°) for each substance involved in the reaction. These values are usually found in tables of thermodynamic data.
3. Apply the formula for the standard entropy change of a reaction: ΔS°rxn = ΣS°products - ΣS°reactants. This involves summing the standard entropy values of the products and subtracting the sum of the standard entropy values of the reactants.
4. Calculate the entropy change using the formula. Ensure that the stoichiometric coefficients from the balanced chemical equation are used to multiply the standard entropy values of each substance.
5. Review the calculated ΔS°rxn value and compare it to the given options to determine which one matches the calculated result.