Determine the standard enthalpy of formation of Fe₂O₃(s) given the thermochemical equations below.

Question

Determine the standard enthalpy of formation of Fe₂O₃(s)given the thermochemical equations below.

Quizplus · Accepted Answer

First, we need to add up the given thermochemical equations in order to obtain the overall balanced equation for the formation of FeS1U1B12S1U1B0OS1U1B13S1U1B0(s):

8Fe1U1B0(s) + S1U1B8(s) + 27H2O1U1B0(l) → Fe8(OH)1539+1U1B0(s) + 8H2(g)
2B2O31U1B0(s) + 3Fe8(OH)1539+1U1B0(s) → 3Fe2O31U1B0(s) + 4B(OH)3(s)
2S1U1B0(g) + 3O21U1B0(g) → 2SO31U1B0(g)
Fe2O31U1B0(s) + 3SO31U1B0(g) → FeS1U1B12S1U1B0OS1U1B13S1U1B0(s)

If we manipulate the above equations, we can obtain the following equation for the formation of FeS1U1B12S1U1B0OS1U1B13S1U1B0(s) from their constituent elements:

14Fe1U1B0(s) + 2B2O31U1B0(s) + 27H2O1U1B0(l) + 11/2O21U1B0(g) + 2S1U1B0(g) → FeS1U1B12S1U1B0OS1U1B13S1U1B0(s) + 8H2(g) + 2B(OH)3(s) + 3SO31U1B0(g)

Now we can use Hess's law and the enthalpies of formation given in the table to calculate the enthalpy of formation of FeS1U1B12S1U1B0OS1U1B13S1U1B0(s):

ΔHf°(FeS1U1B12S1U1B0OS1U1B13S1U1B0(s)) = Σ(nΔHf°products) - Σ(nΔHf°reactants)

= [1(0 kJ/mol) + 1(0 kJ/mol) + 13(-285.8 kJ/mol) + 12(-563.2 kJ/mol) + 1(-1274.8 kJ/mol) + 1(0 kJ/mol)] - [14(0 kJ/mol) + 2(-1094.4 kJ/mol) + 27(-285.8 kJ/mol) + 11/2(0 kJ/mol) + 2(0 kJ/mol)]

= -824.2 kJ/mol-rxn

Therefore, the correct choice is C.

Determine the Standard Enthalpy of Formation of Fe2O3(s)given the Thermochemical

Determine the Standard Enthalpy of Formation of Fe₂O₃(s)given the Thermochemical