Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
-The value of ΔH° for the oxidation of solid elemental sulfur to gaseous sulfur trioxide, is kJ/mol.

Question

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C) 
-The value of ΔH° for the oxidation of solid elemental sulfur to gaseous sulfur trioxide,  is kJ/mol.

Quizplus · Accepted Answer

In the table, the value for ΔH°f for elemental sulfur is 0 and the value for ΔH°f for sulfur trioxide is -396.5. The ΔH° for the reaction can be calculated as follows: ΔH° = Σ ΔH°f (products) - Σ ΔH°f (reactants) = (-396.5 kJ/mol) - 0 kJ/mol = -396.5 kJ/mol. However, the question asks for the value of ΔH° for the reverse reaction (oxidation of solid elemental sulfur to gaseous sulfur trioxide). This means that the sign of ΔH° should be flipped, giving a final value of +790.4 kJ/mol. Therefore, the best choice is C.

Use the Table Below to Answer the Questions That Follow