Answer:
ΔH2=772 kJ
Explanation:
Hello,
In this case, since the change in a reaction's enthalpy is given by the subtraction between the product's enthalpies and the reactant's enthalpies, we notice that the second reaction is the same initial reaction but arranged on the contrary way. In means that if the original reaction has:
ΔH1=−772 kJ
It means that the reaction:
2NaCl → 2Na + Cl2
Has an enthalpy of reaction of:
ΔH2=-(−772 kJ)
ΔH2=772 kJ
As the reactants and products were all inverted, so the enthalpy change has the same number but different sign.
Best regards.
