Energy in Bonding: Mastery Test

Type the correct answer in the box. Express the answer to four significant figures.

Given:
[tex]C + O_2 \rightarrow CO_2[/tex]

\begin{tabular}{|l|c|}
\hline Bond & \begin{tabular}{c}
Bond Energy \\
(kJ/mol)
\end{tabular} \\
\hline [tex]$C = O$[/tex] & 799 \\
\hline [tex]$O = O$[/tex] & 494 \\
\hline
\end{tabular}

Calculate the enthalpy change for the chemical reaction.

The change in enthalpy for the given reaction is [tex]\square[/tex] kilojoules.



Answer :

To calculate the enthalpy change (ΔH) for the given chemical reaction:

[tex]\[ \text{C} + \text{O}_2 \rightarrow \text{CO}_2 \][/tex]

we will use the bond energies provided:

- Bond energy for [tex]\( \text{C}=\text{O} \)[/tex] is 799 kJ/mol.
- Bond energy for [tex]\( \text{O}=\text{O} \)[/tex] is 494 kJ/mol.

### Steps for Calculating the Enthalpy Change:

1. Identify the bonds broken and formed in the reaction.

In this reaction, we are breaking one [tex]\( \text{O}=\text{O} \)[/tex] bond in [tex]\( \text{O}_2 \)[/tex] and forming two [tex]\( \text{C}=\text{O} \)[/tex] bonds in [tex]\( \text{CO}_2 \)[/tex].

2. Determine the total energy required to break the bonds.

- Energy required to break one [tex]\( \text{O}=\text{O} \)[/tex] bond = 494 kJ/mol.

3. Determine the total energy released in forming the new bonds.

- Energy released in forming two [tex]\( \text{C}=\text{O} \)[/tex] bonds = 2 × 799 kJ/mol = 1598 kJ/mol.

4. Calculate the enthalpy change (ΔH).

The enthalpy change ΔH is given by the difference between the energy of the bonds broken and the energy of the bonds formed:

[tex]\( \Delta H = (\text{Energy of bonds broken}) - (\text{Energy of bonds formed}) \)[/tex]

Substituting the values:

[tex]\( \Delta H = 494 \, \text{kJ/mol} - 1598 \, \text{kJ/mol} \)[/tex]

[tex]\( \Delta H = -1104 \, \text{kJ/mol} \)[/tex]

### Final Answer:

The change in enthalpy for the given reaction is [tex]\(-1104\)[/tex] kJ.