Question 8 of 10

Which of the following reactions shows that the formation of [tex]$NO_2[tex]$[/tex] requires [tex]33.1 \, \text{kJ/mol}$[/tex][/tex]?

A. [tex]N(g) + 2O(g) \rightarrow NO_2(g) + 33.1 \, \text{kJ}[/tex]

B. [tex]\frac{1}{2} N_2(g) + O_2(g) + 33.1 \, \text{kJ} \rightarrow NO_2(g)[/tex]

C. [tex]\frac{1}{2} N_2(g) + O_2(g) \rightarrow NO_2(g) + 33.1 \, \text{kJ}[/tex]

D. [tex]N(g) + O(g) + 33.1 \, \text{kJ} \rightarrow NO_2(g)[/tex]



Answer :

To determine which reaction correctly shows the formation of \( NO_2 \) requiring 33.1 kJ/mol, we need to find the reaction where the energy (33.1 kJ/mol) is shown as a reactant.

Let's evaluate each option:

A. \( N(g) + 2O(g) \rightarrow NO_2(g) + 33.1 \text{kJ} \)

In this reaction, 33.1 kJ is shown as a product, indicating that energy is released during the reaction. This means it is an exothermic reaction, which is not what we are looking for.

B. \( \frac{1}{2} N_2(g) + O_2(g) + 33.1 \text{kJ} \rightarrow NO_2(g) \)

In this reaction, 33.1 kJ is shown as a reactant, indicating that energy is required for the formation of \( NO_2 \), which means it is an endothermic reaction. This matches the requirement of the formation of \( NO_2 \) requiring 33.1 kJ/mol.

C. \( \frac{1}{2} N_2(g) + O_2(g) \left. g(m) NO_2(g) + 33.1 \text{kJ} \right. \)

This reaction does not have a proper reaction arrow and is not correctly formatted, so it cannot be considered as the correct option regardless of the position of the energy term.

D. \( N(g) + O(g) + 33.1 \text{kJ} \rightarrow NO_2(g) \)

Although this reaction shows the energy as a reactant, it uses atomic nitrogen (\( N \)) and oxygen (\( O \)), which is not the standard form. Typically, we use molecular nitrogen (\( N_2 \)) and molecular oxygen (\( O_2 \)) in reactions involving the formation of compounds like \( NO_2 \).

Thus, the correct reaction should use molecular nitrogen and oxygen and show the energy as a reactant indicating an endothermic process.

Therefore, the correct answer is:

B. [tex]\( \frac{1}{2} N_2(g) + O_2(g) + 33.1 \text{kJ} \rightarrow NO_2(g) \)[/tex]