Rate of Reaction:
Measures the rate of formation of a product or the rate of removal of a product
Rate = change in measured property / time
The rate of reaction can be found by measuring the gradient of a concentration/time graph (using a tangent if it’s a curve).
Some terms to know in A-Level Chemistry:
Half-life:
The time taken for the concentration of one of the reactants to fall by half
Rate determining step:
In a multi-step reaction this is the slowest step- the one with the highest activation energy.
Activation energy:
Minimum amount of energy that particles need to have if a collision between them is to result in a reaction
- These graphs show how the rate of reaction varies with respect to a particular reactant and is called its order.
- k is the rate constant, [A] is the concentration of reactant in mol dm-3
Zero order reaction
A reaction that is zero order with respect to a reactant is unaffected by concentration. In a zero order reaction, the concentration term for the reactant is raised to the power of zero.
rate= k [reactant]0
rate=k
First order reaction
A reaction is first order with respect to a reactant if the rate of the reaction is proportional to the concentration of that reactant. The concentration term for this reactant is raised to the power of 1 in the rate equation.
rate= k [reactant]1
rate=k [reactant]
This means that doubling the concentration of a reactant doubles the rate of reaction. Rate is proportional to [reactant]. This means a plot of rate vs. concentration produces a straight line through the origin (rate and concentration are directly proportional).If you plot a concentration vs. time graph and then work out the half-life of the reaction then at a constant temperature, the half-life of a first order reaction will be equal wherever it is measured on the graph.
Second order reaction
A reaction is second order with respect to a reactant if the rate of the reaction is proportional to the concentration of that reaction squared. This means that the concentration term for the reactant in the rate equation is raised to the power of 2.
rate= k [reactant]2
This means that doubling the concentration of the reactant increases the rate by a factor of four.
The rate vs. concentration graph for a second order reaction produces a curve.
In summary:
Drafted by Eunice (Chemistry)
References:
https://www.youtube.com/watch?v=SuZkqJ79BKk
https://www.google.com/url?sa=i&url=https%3A%2F%2F2012books.lardbucket.org%2Fbooks%2Fprinciples-of-general-chemistry-v1.0%2Fs18-04-using-graphs-to-determine-rate.html&psig=AOvVaw2Va0sDQR-ljFvM-nyGl8kp&ust=1625502463084000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCICjx9rqyfECFQAAAAAdAAAAABAg