Q68E - Chemistry (OpenStax)

Question

Question: How does the bond energy of \({\rm{HCl(g)}}\) differ from the standard enthalpy of formation of \({\rm{HCl(g)}}\)?

Step-by-Step Solution

Answer

The bond energy differs from standard enthalpy for \({\rm{HCl}}\) as bond energy and enthalpy breaks \({\rm{HCl}}\) into \({\rm{H}}\) and \({\rm{Cl}}\) atoms and, \({{\rm{H}}_{\rm{2}}}\) and \({\rm{Cl}}\), molecules respectively.

Step 1: Concept Introduction

Bond energy gives the measure of the strength of bond in a chemical reaction.

Step 2: Difference in bond energy and standard enthalpy of Hydrochloric Acid

The enthalpy change is when a mole of a substance is created from its elements in their standard states under standard conditions is called enthalpy of formation.

\({\rm{HCl(g)}} \to {{\rm{H}}_{\rm{2}}}{\rm{(g) + Cl(g)}}\)

Bond enthalpy is quite different and is a measure of the strength of an individual bond.

\({\rm{HCl(g)}} \to {\rm{H(g) + Cl(g)}}\)

Bond energy involves breaking of \({\rm{HCl}}\) molecule into \({\rm{H}}\) and \({\rm{Cl}}\) atoms whereas enthalpy of formation involves making of \({\rm{HCl}}\) from \({{\rm{H}}_{\rm{2}}}\) and \({\rm{Cl}}\), molecules.

Therefore, bond energy of \({\rm{HCl}}\) differ from the standard enthalpy of formation of \({\rm{HCl}}\).