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Rates of reaction
Rates of reaction
Reaction rates describe the rate of product of products (or the rate of removal of products) and is expressed mathematically as the change of concentration over time:
rate = d[C] / dt
For most elementary (single step) reactions, rate of the reaction depends on the concentration of the components involved and a rate constant (k).
For a reaction involving multiple steps, the rate of a reaction usually depends on the speed of the rate-limiting step in a reaction.
Order of reaction
Order of reaction
For a reaction, the rate of the reaction depends on the concentration of the components involved and a rate constant (k). The term order of reaction describes the number of components whose concentrations affect the rate of reaction.
Usually reactions are first order with respect to each component involved in the reaction, so the overall order of reaction is the sum of the number of components involved in the reaction step. However, this is not always the case, some reactants may not influence the reaction rate (zero-order in that component), or have multiple molecules involved in the step (leading to second or higher order with respect to that component).
Rate equations
Rate equations
For a simple reaction such as:
A + B --> C
Where the concentrations of the A and B and a rate constant (k) affect the rate in a second order reaction, the rate equation is expressed as:
d[C]/dt = k[A][B]
A graph showing the progress of a reaction with product being formed over time.
A graph showing the progress of a reaction with reagents being consumed over time.
The rate equations for these two systems above differ in the sign of the rate constant, and the y-term which is being expressed. The equations are otherwise the same, with the concentration of the reactants and the rate constant determining the rate of the reaction.
Pseudo-first order kinetics
Pseudo-first order kinetics
Pseudo-first order kinetics
Pseudo-first order kinetics
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