Chapter 5, Problem 79QP

Interpretation Introduction

Interpretation:

The enthalpy of formation for elements ${\text{CaCl}}_{\text{2}}\left(s\right)$ and ${\text{Ag}}_{\text{2}}\text{O}\left(s\right)$ isto be determined.

Concept introduction:

The standard enthalpy for a reaction is the change in enthalpythat occursunder standard conditions, that is, under room temperature and pressure (at 27°C and 1 atm).

The standard enthalpy of the reaction is to be determined using the equation given below:

$\Delta H{°}_{\text{rxn}}={\displaystyle \sum n}\Delta H_{\text{f}}^{\text{°}}\left(\text{products}\right)-{\displaystyle \sum m}\Delta H_{\text{f}}^{°}\left(\text{reactants}\right)$

Here, the stoichiometric coefficients are represented by m for reactants and n for products, and enthalpy of formation under standard conditions is represented by $\Delta H_{\text{f}}^{°}$.

The value of enthalpy of formation of an element is zero at its most stable state.