20) Given the following data:
\[
\begin{array}{ll}
\mathrm{N}_{2}(\mathrm{~g})+\mathrm{O}(\mathrm{g}) \rightarrow 2 \mathrm{NO}(\mathrm{g}) & \Delta \mathrm{H}=180.6 \mathrm{~kJ} \\
\mathrm{~N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{NH}_{3}(\mathrm{~g}) & \Delta \mathrm{H}=-91.8 \mathrm{~kJ} \\
2 \mathrm{H}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) & \Delta \mathrm{H}=-483.7 \mathrm{~kJ}
\end{array}
\]
Calculate the \( \Delta \mathrm{H}^{\circ} \) for the reaction: \( 4 \mathrm{NH}_{3}(\mathrm{~g})+5 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 4 \mathrm{NO}(\mathrm{g})+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \)
Reverse sec Reaction
\( 2 \mathrm{NH}_{3}(\mathrm{~g}) \rightarrow \mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{0}(\mathrm{~g}) \Delta H_{=}-91.8 \mathrm{~kJ} \)
Firet Reaction
\[
\begin{array}{l}
{\left[\mathrm{N}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{NO}(\mathrm{g})\right] \times 2} \\
2 \mathrm{~N}_{2}(\mathrm{~g})+2 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{HNO}(\mathrm{g})
\end{array}
\]
21) Given the following data:
\[
\begin{array}{l}
\mathrm{C}_{6} \mathrm{H}_{4}(\mathrm{OH})_{2}(\mathrm{aq}) \rightarrow \mathrm{C}_{6} \mathrm{H}_{4} \mathrm{O}_{2}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g}) \\
\mathrm{H}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{aq}) \\
\mathrm{H}_{2}(\mathrm{~g})+1 / 2 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \\
\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{l})
\end{array}
\]
\[
\Delta H=+177.4 \mathrm{~kJ}
\]
\[
\Delta H=-191.2 \mathrm{~kJ}
\]
\[
\Delta H=-241.8 \mathrm{~kJ}
\]
\[
\Delta H=-43.8 k J
\]
Calculate the \( \Delta \mathrm{H}^{\circ} \) for the reaction:
\[
\begin{array}{l}
\mathrm{H}^{\circ} \text { for the reaction: } \\
\mathrm{C}_{6} \mathrm{H}_{4}(\mathrm{OH})_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{aq}) \rightarrow \mathrm{C}_{6} \mathrm{H}_{4} \mathrm{O}_{2}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O} \text { (1) }
\end{array}
\]