Question

Use standard enthalpies of formation to calculate ΔH∘rxn for the following reaction. Cr2O3(s)+3CO(g)→2Cr(s)+3CO2(g)

Answer 1

The standard enthalpy of formation of CO2(g) is -393.5 kJ/mol. To calculate ΔH∘rxn for the given reaction, we can use Hess's law and the enthalpy changes of two balanced equations. By adding the enthalpy changes together, we can obtain the desired reaction enthalpy change.

Step-by-step explanation:

The standard enthalpy of formation of CO2(g) is -393.5 kJ/mol. This value represents the change in enthalpy when one mole of CO2 is formed from its constituent elements in their standard states under standard conditions of 298 K and 1 atm pressure. To calculate ΔH∘rxn for the given reaction, we need to use Hess's law and the enthalpy changes of the two balanced equations:

2 CO(g) + O₂(g) → 2 C(s) + 2 CO₂(g) ΔH = +221.0 kJ

C(s) + O₂(g) → CO₂(g) ΔH = -393.5 kJ

By multiplying the second equation by 2 and adding it to the first equation, we can cancel out the carbon and obtain the desired reaction:

2 CO(g) + O₂(g) → 2 C(s) + 2 CO₂(g) ΔH = -393.5 kJ + 2*(+221.0 kJ) = -531.5 kJ