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7. (10 points)

Given the data in the table below, determine [tex]\Delta H^{\circ}_{rxn}[/tex] for the reaction

[tex]\[6 Cl_2(g) + 2 Fe_2O_3(s) \rightarrow 4 FeCl_3(s) + 3 O_2(g)\][/tex]

\begin{tabular}{|l|l|}
\hline
Substance & [tex]\Delta H^{\circ}_{f}\ (kJ/mol)[/tex] \\
\hline
[tex]Cl_2(g)[/tex] & 0.0 \\
\hline
[tex]Fe_2O_3(s)[/tex] & -824.2 \\
\hline
[tex]FeCl_3(s)[/tex] & -399.5 \\
\hline
[tex]O_2(g)[/tex] & 0.0 \\
\hline
\end{tabular}


Sagot :

To find the standard enthalpy change [tex]\(\Delta H^{\circ}_{\text{rxn}}\)[/tex] for the given reaction:
[tex]\[ 6 \text{Cl}_2(g) + 2 \text{Fe}_2\text{O}_3(s) \rightarrow 4 \text{FeCl}_3(s) + 3 \text{O}_2(g), \][/tex]
we need to use the provided standard enthalpy of formation ([tex]\(\Delta H_{f}^{\circ}\)[/tex]) values for each substance involved.

### Step-by-Step Solution:

1. Identify the enthalpy of formation ([tex]\(\Delta H_{f}^{\circ}\)[/tex]) for each substance:

[tex]\[ \begin{aligned} &\text{Cl}_2(g) & : &\quad 0.0 \, \text{kJ/mol} \\ &\text{Fe}_2\text{O}_3(s) & : &\quad -824.2 \, \text{kJ/mol} \\ &\text{FeCl}_3(s) & : &\quad -399.5 \, \text{kJ/mol} \\ &\text{O}_2(g) & : &\quad 0.0 \, \text{kJ/mol} \\ \end{aligned} \][/tex]

2. Use the stoichiometric coefficients from the balanced chemical equation:

[tex]\[ \begin{aligned} &\text{Cl}_2(g) & : &\quad 6 \\ &\text{Fe}_2\text{O}_3(s) & : &\quad 2 \\ &\text{FeCl}_3(s) & : &\quad 4 \\ &\text{O}_2(g) & : &\quad 3 \\ \end{aligned} \][/tex]

3. Calculate the total enthalpy of the reactants:

[tex]\[ \Delta H_{\text{reactants}} = (6 \times 0.0) + (2 \times -824.2) \][/tex]

[tex]\[ \Delta H_{\text{reactants}} = 0 + (-1648.4) = -1648.4 \, \text{kJ} \][/tex]

4. Calculate the total enthalpy of the products:

[tex]\[ \Delta H_{\text{products}} = (4 \times -399.5) + (3 \times 0.0) \][/tex]

[tex]\[ \Delta H_{\text{products}} = -1598.0 + 0 = -1598.0 \, \text{kJ} \][/tex]

5. Calculate the standard enthalpy change of the reaction ([tex]\(\Delta H^{\circ}_{\text{rxn}}\)[/tex]):

[tex]\[ \Delta H^{\circ}_{\text{rxn}} = \Delta H_{\text{products}} - \Delta H_{\text{reactants}} \][/tex]

[tex]\[ \Delta H^{\circ}_{\text{rxn}} = -1598.0 - (-1648.4) \][/tex]

[tex]\[ \Delta H^{\circ}_{\text{rxn}} = -1598.0 + 1648.4 = 50.4 \, \text{kJ} \][/tex]

Thus, the standard enthalpy change for the reaction, [tex]\(\Delta H^{\circ}_{\text{rxn}}\)[/tex], is [tex]\(50.4 \, \text{kJ}\)[/tex].