Question

A certain reaction occurs in two steps as i) $\ce{2SO_{2(g)} + 2NO_{2(g)} -> 2SO_{3(g)} + 2NO_{(g)}}$ ii) $\ce{2NO_{(g)} + O_2(g) -> 2NO_{2(g)}}$

In the reaction,

• A. $\ce{NO_{2(g)}}$ is intermediate
• B. $\ce{NO_{(g)}}$ is intermediate
• C. $\ce{NO_{(g)}}$ is catalyst
• D. $\ce{O_{2(g)}}$ is intermediate

Answer 1

Answer: (B)

$\ce{NO_{(g)}}$ is intermediate

Answer 2

Given,

Step I:

$2 SO_{2}(g) + 2 NO_{2}(g) \to 2 SO_{3}(g) + 2 NO(g)$

Step II: $2 NO(g) + O_{2}(g) \to 2 NO_{2}(g)$

An intermediate formed in the reaction is not a part of the overall reaction.

Net reaction: $2 SO_{2}(g) + O_{2}(g) \to 2 SO_{3}(g)$

As $NO(g)$ formed in the first elementary step is neither a reactant nor a product in the net reaction, it is formed in one elementary step and consumed in the next step. Thus, $NO(g)$ acts as an intermediate.