Rates of reaction - kinetics

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Chemical kinetics is the study of the rates of chemical reactions. A quantitative study of rates leads to the idea of a rate equation. Understanding rate equations helps chemists to control the rate of chemical changes and to explore the mechanisms of chemical reactions. So this topic gives answers to two important questions: 'How fast?' and 'How?'.
 
In this part of the site we answer general questions about the theory of chemical kinetics. We are asked a lot of questions about investigations, especially studies of the rate of reaction of metals with acid. You will find tutorials and FAQs about these investigations at 'Metals + Acids' investigations.
Tutorials on other investigations and general advice on planning and writing up investigations can be found under Practical Investigations.
 
NEW - Summer 2007
We have also now sorted and listed most of the questions we have received on this topic over the years - see Sorted questions on rates of reaction. The unsorted questions also still appear under 'Recently Asked Questions' at the end of this section.
 

back to A2 Chemistry

Tutorials

• Sorted FAQs on Rates of Reaction.
• 'Metals + Acids' investigations
• Logarithms and the rate equation
• Rates from concentration
• Rates and mechanisms: audio tutorial
• How does 'y = mx + c' relate to the Arrhenius equation?

Webguides

• Schoolhouse kinetics reaction
• Key ideas about rates of reaction
• Catalysts and how they work

Recently Asked Questions

• Thanks for your help! I did find that the reaction was first order to peroxydisulphate ions. And a lot of it makes more sense! So from my findings I know that the mechanism will have something like this: I^-(aq) + S₂O₈^2- (aq) -> - - - - - - (rate-determing step) ----- + I^- ----> I₂ (aq) + S₂O₄^2- But i can't think of an intermediate which could be -----? Is it possible to ever know ? Thanks again, very appreciated 280410
• I have done lots of research on the Iodine Clock and am confused! I understand that the overall mechanism of the reaction is: S2O82-(aq) +2I-(aq) --> 2SO42-(aq) + I2(aq) where Iodine is produced The Iodine is then reduced with sodium thiosulfate until the sodium thiosulfate runs out. However, what i don't understand is that we find the I- ions to be first order. Doesn't this mean that the mechanism should only have 1 mol of I- and not 2? Is there are rate determining step within this mechanism where only one mol of I- is present? 200310
• Analysing the results in an iodine and propanone experiment, on the volume of thiosulphate vs time graph: concentration = y axis and x axis = time. Would the concentration be cm³? However, when substituting values I need to use concentrations in mol dm^-3 so how do I change my titre values into mol dm^-3? 110310

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Tests

• Reaction kinetics (A2)

updated: 28 September 2009