ch2416 - bkc revision notes

CH2416 - Kinec Techniques Simple Reacon Kinecs For the reacon; A+B → C - in which the reacon is rst order with respect to B and C; To achieve pseudo-rst order use one rea- gent in large excess over the other. i.e. [B] o >>>[A] 0 This can be ploed in the form; Composion of the Transion State For a single step reacon the rate law provides the em- pirical formula of an intermediate - addive rate terms show compeve pathways; Parallel pathways with the same T.S. will not show as addive terms. Addive terms in the denominator describe a reversi- ble reacon of at least one intermediate, by making each term dominant (i.e. much larger than the other terms in the denominator) in turn it is possible to iden- fy the formulae of the species either side o f the equi- libria. Steady State Approximaon Where an intermediate is only formed in small amounts it can be assumed that d[I]/ dt is equal to 0. Techniques for the Analysis of Rapid Reac- ons Stop-fow - for the study of reacons over 0.1→100 sec. Reagents are mixed in a chamber and analysed immediately. Laser-fash photolysis - for the study of reacons over 1 x 10 -13 → 1 x 10 -2 sec. Re- quires that the reacon can be iniated by light. Propagaon of Errors Kinec studies must be performed with accurate concentraon data and me measurements at a constant and well-dened temperature. For a rst order reacon; -me dependence of k; i.e. a 1% error in t= 1% error in k -concentraon dependence of k; I.e. a xed error in [Q] has a higher impact at lower values of t. -temperature dependence of k;

ch2416 - bkc revision notes

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