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This question is about hydrogen and compounds of hydrogen.

Figure 3 shows the displayed formulae for the reaction between hydrogen and chlorine.

Figure 3
[tex]\[ H - H + Cl - Cl \longrightarrow 2 H - Cl \][/tex]

Table 4 shows the bond energies.

Table 4
\begin{tabular}{|l|c|c|c|}
\hline Bond & [tex]$H - H$[/tex] & [tex]$Cl - Cl$[/tex] & [tex]$H - Cl$[/tex] \\
\hline \begin{tabular}{l}
Bond energy in \\
kJ/mol
\end{tabular} & 436 & 346 & 432 \\
\hline
\end{tabular}

Using Table 4, calculate the total energy change in the reaction shown in Figure 3.
Tick [tex]$(\checkmark)$[/tex] one box.
[1 mark]

A. [tex]\[ 436 + 346 + 432 \, \text{kJ/mol} \][/tex] [tex]$\square$[/tex]
B. [tex]\[ 436 + 346 + (2 \times 432) \, \text{kJ/mol} \][/tex] [tex]$\square$[/tex]
C. [tex]\[ 436 + 346 - 432 \, \text{kJ/mol} \][/tex] [tex]$\square$[/tex]
D. [tex]\[ 436 + 346 - (2 \times 432) \, \text{kJ/mol} \][/tex] [tex]$\square$[/tex]



Answer :

To solve this question, we need to calculate the net energy change for the reaction between hydrogen and chlorine as shown:

[tex]\[ H - H + Cl - Cl \longrightarrow 2 H - Cl \][/tex]

First, we need to break the bonds of [tex]\(H - H\)[/tex] and [tex]\(Cl - Cl\)[/tex]. These are the bond energies we must consider first:
- The bond energy for [tex]\(H - H\)[/tex] is [tex]\(436 \text{ kJ/mol}\)[/tex].
- The bond energy for [tex]\(Cl - Cl\)[/tex] is [tex]\(346 \text{ kJ/mol}\)[/tex].

The total energy required to break these bonds (energy input) is:
[tex]\[ 436 + 346 \text{ kJ/mol} = 782 \text{ kJ/mol} \][/tex]

Next, new bonds are formed to create [tex]\(2 \times H - Cl\)[/tex]:
- The bond energy for [tex]\(H - Cl\)[/tex] is [tex]\(432 \text{ kJ/mol}\)[/tex].

Since we form two [tex]\(H - Cl\)[/tex] bonds, the total energy released (energy output) is:
[tex]\[ 2 \times 432 \text{ kJ/mol} = 864 \text{ kJ/mol} \][/tex]

Finally, we calculate the net energy change for the reaction:
[tex]\[ \text{Net energy} = \text{Energy input} - \text{Energy output} \][/tex]
[tex]\[ \text{Net energy} = 782 \text{ kJ/mol} - 864 \text{ kJ/mol} = -82 \text{ kJ/mol} \][/tex]

The correct answer should reflect the energy changes we calculated. Out of the given options, the option that correctly represents our calculations is:
[tex]\[ 436 + 346 - (2 \times 432) \text{ kJ/mol} \][/tex]

Thus, the box with:
[tex]\[ \checkmark \quad 436 + 346 - (2 \times 432) \text{ kJ/mol} \][/tex]
is the correct choice.

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