Calculate the energy change for the reaction S(s)+O2(g) ⟶SO2(g) from the following: 2 S(s)

step 1 We'll take our first equation, 2S solid plus 3O2 gas producing 2SO3 gas. Enthalpy here is minus

Calculate the energy change for the reaction S(s)+O2(g)...

Calculate the energy change for the reaction $\mathrm{S}(s)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{SO}_{2}(g)$ from the following: $$ \begin{array}{ll} 2 \mathrm{~S}(s)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{SO}_{3}(g) & \Delta H=-792 \mathrm{~kJ} \\ 2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{SO}_{3}(g) & \Delta H=-198 \mathrm{~kJ} \end{array} $$

Calculate the energy change for the reaction $\mathrm{S}(s)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{SO}_{2}(g)$ from the following:
$$
\begin{array}{ll}
2 \mathrm{~S}(s)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{SO}_{3}(g) & \Delta H=-792 \mathrm{~kJ} \\
2 \mathrm{SO}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{SO}_{3}(g) & \Delta H=-198 \mathrm{~kJ}
\end{array}
$$

Key Concepts

Hess's Law

Hess's Law is the principle that the total enthalpy change for a chemical reaction is the same regardless of the route taken, provided the initial and final conditions are identical. This allows us to calculate the enthalpy change of a reaction by algebraically combining other reactions with known enthalpy changes, making it a fundamental tool in thermochemistry.

Enthalpy Change (?H)

Enthalpy change is the heat absorbed or released during a chemical reaction at constant pressure. It is a crucial concept in thermochemistry for understanding the energetic profile of reactions, where negative values indicate exothermic reactions and positive values indicate endothermic reactions.

Reaction Stoichiometry

Reaction stoichiometry involves the quantitative relationships between reactants and products in a balanced chemical equation. It is essential for ensuring that the proper proportions are used when combining reactions or scaling them, which is critical when applying Hess's Law to determine overall enthalpy changes.

Thermochemical Equations

Thermochemical equations are balanced chemical equations that include the enthalpy changes associated with the reactions. They provide a concise summary of both the chemical transformation and the corresponding energy changes, allowing for systematic manipulation and combination in calculations such as those required by Hess's Law.

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