For the reaction NO2+CO→CO2+NO, the experimental rate expression is −dc/dt=kNO22. Find the number of molecules of CO involved in the slowest step.

Reaction between NO2 and CONO2(g)+CO(g)⟶NO(g)+CO2(g) Rate =kNO22The experimental observations reveal that the rate of reaction is proportional to the square of the concentration of nitrogen peroxide. This indicates that the rate- determining step in the mechanism of this reaction must be independent of the concentration of CO. Keeping this in mind, e mechanism of the reaction may be suggested as:Although the above reaction proceeds through two steps but the rate of overall reaction is determined by the first step which is the slower of the two steps. Accordingly, theexperimentally observed rate of the reaction is given by the expression: Rate =kNO22