This preview shows pages 1–4. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Chapter 12: Chemical Kinetics, Part 2 ZeroOrder Reactions (or zeroth order) For a zeroorder reaction , the rate is independent of the concentration of the reactant(s). (of course, there does have to be some reactant present in order for any rxn to occur) One example is the following rxn: As it is zeroorder, the rate law is: But the rate is also equal to the change in a reactant over the change in time, so we may write: Rearranging we get: Integrating we get: Rearranging to get an equation of a line gives us this: A plot of [ A ] t versus t is a straight line with slope  k and intercept [ A ] 0 (sometimes called [A] i . Here are typical examples of zeroorder graphs: Halflife , t 1/2 , is the time required for the concentration of a reactant to decrease to half its original value. That is, half life, t 1/2 , is the time required for [ A ] to reach 0.5[ A ] . Mathematically, FirstOrder Reactions For a firstorder reaction , the rate doubles as the concentration of a reactant doubles. Therefore: Integrating: We get: Rearranging: An alternative form: A plot of ln[ A ] t versus t is a straight line with slope  k and intercept ln[ A ] . Note that in this equation we use the natural logarithm, ln (log to the base e ). Here are typical examples of graphs for 1storder rxns: Problem (see handout): HalfLife for 1 st order rxns: Mathematically t 1/2 is: Note that the halflife of a firstorder reaction is independent of the initial concentration of the reactant. Problem (see handout): SecondOrder Reactions A secondorder reaction is one whose rate depends on the reactant concentration to the second power or on the concentration of two reactants, each raised to the first power. power or on the concentration of two reactants, each raised to the first power....
View
Full
Document
 Fall '06
 Dr.Samples
 Kinetics

Click to edit the document details