Nitrosyl chloride, NO2Cl, forms in the atmosphere from the reaction between nitrogen dioxide and molecular chlorine:
2 NO2(g) + Cl2(g) → 2 NO2Cl(g)
Field observations indicate that traces of gaseous Cu+ ions (produced from particulate matter) greatly increase the rate of formation of NO2Cl. A proposed catalytic mechanism is shown below.
Step 1 Cu+ + NO2 → Cu(NO2)+ (fast)
Step 2 Cu(NO2)+ + Cl2 → CuCl2+ + NO2Cl (slow)
Step 3 CuCl2+ + NO2 → Cu+ + NO2Cl (fast)
(The copper-containing species are present only in trace amounts and are regenerated.)
(a) Describe the role played by Cu+ in the overall reaction. In your answer, refer explicitly to its consumption and regeneration in the elementary steps.
(b) Explain why Step 2, rather than the uncatalyzed bimolecular collision between NO2 and Cl2, is now the rate-determining process for the overall reaction.
(c) Using the mechanism, predict the overall order of the reaction with respect to Cu+ and justify your prediction without performing an explicit algebraic derivation.
(d) State one experimental observation (other than an increased rate) that would support the claim that Cu+ acts as a true catalyst in this system.