Chemistry - Chemical Kinetics Question with Solution | TestHub

The order of a reaction is determined experimentally by its rate law.

For the decomposition of hydrogen peroxide, the rate law is Rate = $k[{\text{H}}_2{\text{O}}_2]$. It is a first-order reaction.

For the thermal decomposition of acetaldehyde, the rate law is Rate = $k[{\text{CH}}_3\text{CHO}{]}^{1.5}$. It is a fractional-order (1.5) reaction.

For the reaction between ${\text{NO}}_2$ and ${\text{F}}_2$, the mechanism involves a slow rate-determining step: ${\text{NO}}_2+{\text{F}}_2\to {\text{NO}}_2\text{F}+\text{F}$. The rate law is Rate = $k[{\text{NO}}_2][{\text{F}}_2]$. The overall order is $1+1=2$, making it a second-order reaction.

For the reaction between $\text{NO}$ and ${\text{H}}_2$, the rate law is Rate = $k[\text{NO}{]}^2[{\text{H}}_2]$. The overall order is $2+1=3$, making it a third-order reaction.

Thus, $2{\text{NO}}_{2(g)}+{\text{F}}_{2(g)}\to 2{\text{NO}}_2{\text{F}}_{(g)}$ is the correct example of a second-order reaction.

Answer: $2{\text{NO}}_{2(g)}+{\text{F}}_{2(g)}\to 2{\text{NO}}_2{\text{F}}_{(g)}$