Nitrogen dioxide reacts with carbon monoxide: NO₂(g) + CO(g) → NO(g) + CO₂(g)…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Nitrogen dioxide reacts with carbon monoxide: . The mechanism has two steps. Step 1, slow: . Step 2, fast: . (a) Show that the steps add up to the overall equation. (b) Name the intermediate. (c) Give the molecularity of each step. (d) Write the rate law and the overall order. (e) Give the unit of , with time in seconds.
Need a reminder? The key ideaShow
Molecularity is the number of particles that collide in an elementary step, and it is 1, 2 or 3. For an elementary step the rate law follows from the equation. For a complex reaction, the rate law is that of the slow step, the rate-determining step.
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
(a) Adding the steps. The sum is . Cancel one on each side and the on each side. What is left is .
(b) The intermediate. forms in step 1 and is used up in step 2, so it does not appear in the overall equation.
(c) Molecularity. Both steps have two particles that collide, so both are bimolecular.
(d) The rate law. The slow step sets the rate: . The overall order is 2. Carbon monoxide does not appear, because it reacts only in the fast step.
(e) The unit. For order 2 it is .
Answer: the intermediate is , both steps are bimolecular, rate , the order is 2, and is in .
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