Chemistry

Chemistry

Problem

For a chemical reaction that has an enthalpy change of ΔH∘\Delta H^{\circ}, which of the following describes what happens to ΔH∘\Delta H^{\circ} if every stoichiometric coefficient in the balanced equation is multiplied by 3? a) ΔH∘\Delta H^{\circ} is divided by 3. b) ΔH∘\Delta H^{\circ} is multiplied by 3. c) ΔH∘\Delta H^{\circ} is unchanged. d) ΔH∘\Delta H^{\circ} changes sign but retains the same magnitude.
Intuitive explanation

Enthalpy is an extensive property—it depends on the amount of substance involved. When you multiply all stoichiometric coefficients by 3, you're tripling the scale of the reaction: three times as much reactant converts to three times as much product. Since enthalpy change scales directly with the amount of reaction, ΔH∘\Delta H^{\circ} will also triple. Think of it like this: burning one mole of fuel releases a certain amount of heat; burning three moles releases three times that heat.

Intuitive explanation

Enthalpy is an extensive property—it depends on the amount of substance involved. When you multiply all stoichiometric coefficients by 3, you're tripling the scale of the reaction: three times as much reactant converts to three times as much product. Since enthalpy change scales directly with the amount of reaction, ΔH∘\Delta H^{\circ} will also triple. Think of it like this: burning one mole of fuel releases a certain amount of heat; burning three moles releases three times that heat.

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