A proposed reaction mechanism for the formation of nitrosyl bromide is: (1) NO(g) + Br2(g) NOBr2(g — Kinetics Chemistry Question
Problem Context
A proposed reaction mechanism for the formation of nitrosyl bromide is:
(1) NO(g) + Br2(g) NOBr2(g)
(2) NOBr2(g) + NO(g) 2NOBr(g)
Write the overall equation for this reaction.
Model Answer
2 NO + Br2 2 NOBr
Determine the rate law for this reaction if the rate determining step is the
i. first step in the mechanism.
Model Answer
Rate = k1 × [NO] × [Br2]
ii. second step in the mechanism.
Model Answer
Rate = k2 × [NOBr2] × [NO] Rate = k2 × K[NO][Br2][NO]
State and explain how the rate determining step could be identified experimentally. Describe the experiments to be performed and the results expected for each mechanism.
Model Answer
The [NO] can be varied at constant [Br2] while studying rate.
If first step is limiting: Rate [NO]
If second step is limiting: Rate will increase [NO]2
Sketch and label a potential energy diagram for each of the mechanisms in b., showing and labeling each step for this exothermic reaction.
State and explain using chemical principles and graphs how a temperature increase would affect the reaction rate.
Model Answer
T↑ will increase reaction rate since at higher T more molecules will have the energy equal or greater than Ea (necessary activation energy).