Chapter 15.3, Problem 26SSC

Interpretation Introduction

Interpretation:

A balanced thermo-chemical equation for the combustion of ethanol is to be written.

Concept introduction:

Thermo-chemical equation: A thermo-chemical equation of a chemical reaction is a balanced stoichiometric equation that includes the enthalpy of reaction $\left(\Delta H\right)$.

Answer to Problem 26SSC

The chemical equation for the combustion of ethanol is:

${\mathrm{C}}_2{H}_{5}OH+O_2\stackrel{}{\to }C{O}_2+H_{2}O$

The number of atoms on both sides of the chemical reaction needs to be balanced.

${\mathrm{C}}_2{H}_{5}OH\left(l\right)+3O_2\left(g\right)\stackrel{}{\to }2C{O}_2\left(g\right)+3H_{2}O\left(l\right)$

Thermo-chemical equation includes the enthalpy of reaction.

${\mathrm{C}}_2{H}_{5}OH\left(l\right)+3O_2\left(g\right)\stackrel{}{\to }2C{O}_2\left(g\right)+3H_{2}O\left(l\right)+1367kJ$

Explanation of Solution

The following steps are needed to write the thermochemical equation of the combustion of ethanol:

• Write the chemical reaction for combustion of ethanol
• Balance the number of atoms on both the sides of the chemical reaction and mention the state of reactants and products.
• Add the enthalpy of reaction to the product as the combustion of ethanol is an exothermic reaction.

Conclusion

Thermochemical equation of the combustion of ethanol is:

${\mathrm{C}}_2{H}_{5}OH\left(l\right)+3O_2\left(g\right)\stackrel{}{\to }2C{O}_2\left(g\right)+3H_{2}O\left(l\right)+1367kJ$