Chapter 18, Problem 36PS

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074

Chapter
Section

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074
Textbook Problem

# Using values of ΔfG°, calculate ΔrG° for each of the following reactions at 25 °C. Which are product- favored at equilibrium? (a) HgS(s) + O2(g) → Hg(ℓ) + SO2(g) (b) 2 H2(g) + 3 O2(g) → 2 H2O(g) + 2 SO2(g) (c) SiCl4(g) + 2 Mg(s) → 2 MgCl2(s) + Si(s)

(a)

Interpretation Introduction

Interpretation:

The value of ΔrG for the given reaction HgS(s)+O2(g)Hg(l)+SO2(g) at 25 °C should be calculated and should be identified that whether the reaction is product-favoured at equilibrium.

Concept introduction:

The Gibbs free energy or the free energy change is a thermodynamic quantity represented by ΔG. It can be calculated in a similar manner as entropy and enthalpy.  The expression for the free energy change is:

ΔrG°=nΔfG°(products)nΔfG°(reactants)

Explanation

The standard free energy change for the reaction of HgS(s) and O2(g) is calculated below.

The Appendix L referred for the standard free energy change values.

The standard free energy change value of HgS(s) is 50.6 kJ/mol.

The standard free energy change value of O2(g) is 0 kJ/mol.

The standard free energy change value of SO2(g) is 300.13 kJ/mol.

The standard free energy change value of Hg(l) is 0 kJ/mol.

The balanced chemical equation is,

HgS(s)+O2(g)Hg(l)+SO2(g)

The expression for the free energy change is:

ΔrG°=nΔfG°(products)nΔfG°(reactants)=[[(1 mol Hg(l)/mol-rxn)ΔfG°[Hg(l)]+(1 mol SO2(g)/mol-rxn)ΔfG°[SO2(g)]][(1 mol HgS(s)

(b)

Interpretation Introduction

Interpretation:

The value of ΔrG for the given reaction HgS(s)+O2(g)Hg(l)+SO2(g) at 25 °C should be calculated and should be identified that whether the reaction is product-favoured at equilibrium.

Concept introduction:

The Gibbs free energy or the free energy change is a thermodynamic quantity represented by ΔG. It can be calculated in a similar manner as entropy and enthalpy.  The expression for the free energy change is:

ΔrG°=nΔfG°(products)nΔfG°(reactants)

(c)

Interpretation Introduction

Interpretation:

The value of ΔrG for the given reaction SiCl4(g)+2Mg(s)2MgCl2(s)+Si(s) at 25 °C should be calculated and should be identified that whether the reaction is product-favoured at equilibrium.

Concept introduction:

The Gibbs free energy or the free energy change is a thermodynamic quantity represented by ΔG. It can be calculated in a similar manner as entropy and enthalpy.  The expression for the free energy change is:

ΔrG°=nΔfG°(products)nΔfG°(reactants)

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