Question

Using ∆rH° to calculate ∆fH°. Include steps, please. Correct answer according to the answer sheet is -1346.4 kJ mol⁻¹.

A) ΔfH°=−1346.4kJ mol⁻¹
B) ΔfH°=1346.4kJ mol⁻¹
C) ΔfH°=−1346.4J g⁻¹
D) ΔfH°=1346.4J g⁻¹

Answer 1

To calculate the standard enthalpy of formation (ΔfH°), one sums the standard enthalpies of formation of the products and subtracts the sum of the enthalpies of formation of the reactants. The correct answer according to the provided information is -1346.4 kJ mol⁻¹.

Step-by-step explanation:

The question is asking how to use the standard enthalpy of reaction (ΔrH°) to calculate the standard enthalpy of formation (ΔfH°). The standard enthalpy of formation of a compound is the enthalpy change when one mole of the compound is formed from its elements in their standard states. To find ΔfH°, one typically needs to have the equation for the formation of the compound from its elements and the standard enthalpies of formation for each reactant and product. However, based on the provided information, we are to find ΔfH° through alternative given data. The correct answer matches option A) ΔfH° = -1346.4 kJ mol⁻¹, which suggests that the calculation has been previously performed using a method similar to the Hess's Law, where one sums the enthalpies of formation of the products and subtracts the sum of the enthalpies of formation of the reactants.