Chapter 15, Problem 91A

Interpretation Introduction

Interpretation:

Thermochemical reaction for the formation of aluminum chloride is to be written.

Concept introduction:

Thermochemical equation: It is the balanced chemical equation that includes the physical states of all the reactants and products and their energy change. Thermochemical equation is usually expressed as change in enthalpy, $\text{ΔH}$.

Answer to Problem 91A

The balanced thermochemical reaction for the formation of aluminum chloride is

${\text{2Al(s)+3Cl}}_{\text{2}}^{}\text{(g)}\to {\text{2AlCl}}_{\text{3}}^{}\text{+Heat}$

Explanation of Solution

Since, heat is given so the reaction is a exothermic reaction with the value of $\text{ΔH=}\text{-704kJ/mol}$

Therefore, for exothermic reaction $\text{ΔH<0}$.

Conclusion

Using Thermodynamics’ law for exothermic reaction $\text{ΔH>0}$, $\text{ΔH}\text{is}\text{negative}$ and for endothermic reaction $\text{ΔH>0}$ and $\text{ΔH}\text{is}\text{negative}$.