7.4 Molecularity: · Part 2

Example Consider the oxidation of nitric oxide to form NO 2NO(g) + O (g) 2NO (g) (a). Express the rate of the reaction in terms of changes in the concentration of NO,O and NO . (b). At a particular instant, when [O ] is decreasing at . mol L s − at what rate is [NO ] increasing at that instant? Solution: a) Rate - d[NO] dt - d[O ] dt d[NO ] dt b) -d[O ] dt d[NO ] dt = d[NO ] dt x -d[O ] dt x mol L s  = . mol L s Evaluate yourself ). Write the rate expression for the following reactions, assuming them as elementary reactions. i) 3A + 5B 4CD ii) X + Y 2XY ). Consider the decomposition of N O (g) to form NO (g) and O (g) . At a particular instant N O disappears at a rate of . x mol dm s - - - . At what rates are NO and O formed? What is the rate of the reaction? Example . What is the order with respect to each of the reactant and overall order of the following reactions? (a). Br BrO H aq aq aq Br 3H O ( ) ( ) l l The experimental rate law is Rate = k Br BrO H ][ ][ (b).  CH CHO CH CO ( ) ( ) ( ) g g g ∆ the experimental rate law is Rate = k CH CHO Solution: a) First order with respect to Br − , first order with respect to BrO and second order with respect to H + . Hence the overall order of the reaction is equal to + + = b) Order of the reaction with respect to acetaldehyde is and overall order is also Example . The rate of the reaction x + 2y product → is