Chemical Kinetics

Some rate laws depend on the concentration of more than one species. For instance, oxidation of iodide ions by persulfate ions: Rate of consumption I^- = k[S₂O₈^2-][I^-]. In such cases, the analysis can be simplified by ensuring that one species remains at the same _________ during the reaction so it can be used as a ______.
- concentration
- constant
In rate laws that depend on the concentration of more than one species, explain a technique used to keep one of the species constant.

Starting the reaction with one of the species in such a high concentration that their concentration barely changes in the course of the reaction.
In the case of the oxidation of iodide ions by persulfate ions: Rate of consumption I- = k[S₂O₈^2-][I^-], if we started with so much [S₂O₈^2-] that it was practically constant throughout our reaction, what would the rate of consumption of I^- be? What is k'? What order of reaction do we have know?
- Rate of consumption of I^- = k'[I^-]
- k' is the value k[S₂O₈^2-], which is another constant
- We have gone from a second order reaction to a pseudo-first order reaction
t1/2

half life; it is the time needed for the concentration of a substance to fall one-half its initial value
Write an equation that shows the relation between the rate constant and the half-life of a reactant in a first order reaction. It should show that the greater the rate constant, the ______ the half-life of a substance.

shorter

t1/2 = ln2/k

Author

Anonymous

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Card Set

Chemical Kinetics

Description

Ch 15 pt 2

Updated

2017-02-16T03:34:24Z

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