Chapter 5, Problem 116SCQ

### 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

# Calculate ΔrH° for the reaction2 C(s) + 3 H2(g) + ½ O2(g) → C2H5OH(ℓ)given the information below.C(s) + O2(g) → CO2(g)ΔrH° = −393.5 kJ/mol-rxn2 H2(g) + O2(g) → 2 H2O(ℓ)ΔrH° = −571.6 kJ/mol-rxnC2H5OH(ℓ) + 3 O2(g) → 2 CO2(g) + 3 H2O(ℓ)ΔrH°= −1367.5 kJ/mol-rxn

Interpretation Introduction

Interpretation:

The enthalpy change of reaction has to be determined.

Concept Introduction:

The standard enthalpy of formation is the enthalpy change for the formation of 1mol of the compound directly from its component elements in their standard states.

Enthalpy change for the reaction ΔrH0=ΣnΔfH0(products)-ΣnΔfH0(reactants)

Explanation

Given equations are solved to get the required equation.

The 1st equation is multiplied by 2, we get,

â€‚Â 2Câ€‰+â€‰2O2â€‰â†’â€‰2CO2Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Î”rH0=-787kJ/mol

Dividing equation 2 by 2, and multiplying by 3 we get

â€‚Â 3H2â€‰+â€‰3/2O2â€‰â†’â€‰3H2OÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  Î”rH0=-857

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