Chapter 24, Problem 24PS

### 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

# The chemical equation for the fermentation of glucose into ethanol isC6H12O6(s) → 2 C2HsOH(ℓ)+ 2 CO2(g)Using ∆fH° values at 25 °C, calculate ∆rH° for this reaction. (See Question 23 for ∆fH° for glucose.)

Interpretation Introduction

Interpretation:

The value of ΔrH° for the given fermentation reaction of glucose into ethanol has to be calculated.

C6H12O6(s)2C2H5OH(l)+2CO2(g)

Concept introduction:

The change in the enthalpy of a reaction when reactant is converted into product under standard conditions is called standard enthalpy of reaction.

The expression for standard enthalpy of reaction is,

ΔrH°=nΔfH°(products)nΔfH°(reactants) (1)

Here, ΔfH° is the standard enthalpy of formation and n is the number of moles of reactant and product in the balanced chemical reaction.

Explanation

The value of Î”rHÂ° for the fermentation reaction of glucose into ethanol is calculated below.

Given:

Refer to Appendix L for the values of standard enthalpy of formation.

The standard enthalpy of formation of C6H12O6(s) is âˆ’1273.3Â kJ/mol.

The standard enthalpy of formation of C2H5OH(l) is âˆ’277Â kJ/mol.

The standard enthalpy of formation of CO2(g) is âˆ’393.5Â kJ/mol.

The given balanced chemical equation is:

â€‚Â C6H12O6(s)â†’2C2H5OH(l)+2CO2(g)

The Î”rHÂ° can be calculated by the following expression,

Î”rHÂ°=âˆ‘nÎ”fHÂ°(products)âˆ’âˆ‘nÎ”fHÂ°(reactants)=[[(2Â molÂ CO2(g)/mol-rxn)Î”fHÂ°[CO2(g)]+(2Â molÂ C2H5OH(l)/mol-rxn)Î”f

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