Question

Calculate the enthalpy of reaction using bond enthalpies for the following reaction: Cl₂(g) + 2H₂O(g) → 4HCl(g) + O₂(g)

Answer 1

Bond enthalpy of $Cl-Cl =243KJ/mol$

Bond enthalpy of $O-H=460KJ/mol$

Bond enthalpy of $H-Cl=432KJ/mol$

Bond enthalpy of $O-O=498KJ/mol$

The reaction is:

$Cl_2(g) + 2H_2O(g) → 4HCl(g) + O_2(g)$

Ethalpy of reaction$=$ Total Bond energy of reactants$-$ Total Bond energy of products$=(243+2\times(2\times 460)-4\times 432-498)=-183KJ/mol$

Negative sign represents it is an exothermic reaction.