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The chemical reaction that causes chromium to corrode in air is given by 4Cr+3O2→2Cr2O3 in which at 298 K ΔH∘rxn = −2256 kJ ΔS∘rxn = −549.1 J/K Part A What is the standard Gibbs free energy for this reaction? Assume the commonly used standard reference temperature of 298 K.

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Answer:

-2092 kJ

Explanation:

Let's consider the chemical reaction that causes chromium to corrode in air.

4 Cr + 3 O₂ → 2 Cr₂O₃

We can calculate the standard Gibbs free energy (ΔG°) using the following expression.

ΔG° = ΔH° - T × ΔS°

where,

  • ΔH°: standard enthalpy of the reaction
  • T: absolute temperature
  • ΔS°: standard entropy of the reaction

ΔG° = -2256 kJ - 298 K × (-0.5491 kJ/K)

ΔG° = -2092 kJ

Answer:

The standard gibbs free energy for this reaction is -2092.4 kJ

Explanation:

Step 1: Data given

Temperature = 298 K

ΔH° rxn = −2256 kJ

ΔS° rxn = −549.1 J/K

Step 2: The balanced equation

4Cr + 3O2 → 2Cr2O3

Step 3:

The formula for the gibbs free energy is:

ΔG° = ΔH° - T * ΔS°

⇒with ΔG° = the gibbs free energy for this reaction = TO BE DETERMINED

⇒with ΔH° = the standard enthalpy of the reaction  = −2256 kJ

⇒with T = the temperature of the reaction in Kelvin = 298 K

⇒with ΔS°  = standard entropy of the reaction = −549.1 J/K

ΔG° = -2256 kJ - 298 K* (-0.5491 kJ/K)

ΔG° = -2256 kJ + 163.6318 kJ

ΔG° = -2092.4 kJ

The standard gibbs free energy for this reaction is -2092.4 kJ

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