Draw an enthalpy cycle to calculate the enthalpy change of formation of ethanol, ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$, using enthalpy changes of combustion.

Calculate a value for $∆{\mathrm{H}}_{\mathrm{f}}^{°}\left[{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{l}\right)\right]$ using the following data:

$$\begin{gathered} ∆{\mathrm{H}}_{\mathrm{c}}^{°}\left[\mathrm{C}\left(\mathrm{graphite}\right)\right]=-393.5 \mathrm{kJ} {\mathrm{mol}}^{-1}. \\ ∆{\mathrm{H}}_{\mathrm{c}}^{°}\left[{\mathrm{H}}_2\left(\mathrm{g}\right)\right]=-285.8 \mathrm{kJ} {\mathrm{mol}}^{-1}. \\ ∆{\mathrm{H}}_{\mathrm{c}}^{°}\left[{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{l}\right)\right]=-1367.3 \mathrm{kJ} {\mathrm{mol}}^{-1}. \end{gathered}$$

Look at this equation.

$3\mathrm{Mg}\left(\mathrm{s}\right)+{\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)\to 2\mathrm{Fe}\left(\mathrm{s}\right)+3\mathrm{MgO}\left(\mathrm{s}\right)$.

Which one of the following gives the correct value for the enthalpy change of this reaction?

Use the information in Figure and the information below to demonstrate that the average bond energy of the $\mathrm{C}-\mathrm{H}$ bond is $415.9 \mathrm{kJ} {\mathrm{mol}}^{-1}$.

$$\begin{gathered} ∆{\mathrm{H}}_{\mathrm{f}}^{°}\left[{\mathrm{CH}}_4\right]=-74.8 \mathrm{kJ} {\mathrm{mol}}^{-1}. \\ ∆{\mathrm{H}}_{\mathrm{at}}^{°}\left[\frac{1}{2}\mathrm{H}\right]=+218 \mathrm{kJ} {\mathrm{mol}}^{-1}. \\ ∆{\mathrm{H}}_{\mathrm{at}}^{°}\left[\mathrm{C}\left(\mathrm{graphite}\right)\right]=+716.7 \mathrm{kJ} {\mathrm{mol}}^{-1}. \end{gathered}$$

Look at this equation.

${\mathrm{CH}}_4\left(\mathrm{g}\right)+2{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$.

Which one of the following statements is completely correct?

Calculate the standard enthalpy change of combustion of methane using the following bond energies:

$$\begin{gathered} \mathrm{E}\left(\mathrm{C}-\mathrm{H}\right)=+412 \mathrm{kJ} {\mathrm{mol}}^{-1}. \\ \mathrm{E}\left(\mathrm{O}=\mathrm{O}\right)=+496 \mathrm{kJ} {\mathrm{mol}}^{-1}. \\ \mathrm{E}\left(\mathrm{C}=\mathrm{O}\right)=+805 \mathrm{kJ} {\mathrm{mol}}^{-1}. \\ \mathrm{E}\left(\mathrm{O}-\mathrm{H}\right)=+463 \mathrm{kJ} {\mathrm{mol}}^{-1}. \end{gathered}$$