Nitrogen monoxide, NO(g), reacts with hydrogen, H2(g), under certain conditions. 2NO(g) + 2H2(g) → N2(g) + 2H2O(g)

1. (a)Define the term rate of reaction.[1]
2. (b)Identify a change in the reaction mixture that would enable the rate of this reaction to be studied.[1]
3. (c)The rate equation for this reaction is given. rate = k[NO]2[H2] The result of an experiment in which NO reacted with H₂ is shown in the table. initial [NO]/mol dm-3 | initial [H2]/moldm-³ | initial rate of reaction/mol dm-³ s-1 --- | --- | --- 2.50 x 10-3 | 2.50 x 10-3 | 1.27 x 10-3 Use the data and the rate equation to calculate a value for the rate constant k. Give the units of k.[2]
4. (d)A second experiment is performed at the same temperature. The initial concentration of H2(g) is 4.60 x 10-3 mol dm-3. The initial rate of the reaction is 2.31 x 10-3 mol dm-3 s-1. Calculate the initial concentration of NO(g).[1]
5. (e)State the order of the reaction with respect to NO(g) and with respect to H2(g), and the overall order of the reaction.[1]
6. (f)(i)The reaction is believed to proceed in three steps. 1 2NO → N2O2 2 N2O2 + H₂ → N2O + H₂O 3 N2O + H2 → N₂ + H₂O Deduce which of the three steps is the rate-determining step.[1]
7. (f)(ii)Explain your answer to (i).[1]
8. (g)(i)A third experiment is performed under different conditions. A small amount of H2(g) of concentration 0.0200 moldm-³ is mixed with a large excess of NO(g). The concentration of H2(g) is found to have a constant half-life of 2.00 seconds under the conditions used. Define the term half-life.[1]
9. (g)(ii)Use the axes below to construct a graph of the variation in the concentration of H2(g) during the first 6 seconds under the conditions used. [Figure showing blank graph axes for [H2] vs time][2]
10. (h)(i)NO(g) acts as a catalyst in the oxidation of atmospheric sulfur dioxide. Give two equations to describe how NO(g) acts as a catalyst in this process.[1]
11. (h)(ii)Explain why NO(g) can be described as a catalyst in this reaction.[1]
12. (h)(iii)Describe, with the aid of an equation, an environmental consequence of the oxidation of atmospheric sulfur dioxide.[1]