Rate Equations

Question 1

How do you work out rate of reaction from a graph?

Answer 1

You use the gradient of the graph

Gradient = change in y / change in x

Question 2

For a general reaction, what is the rate equation?

Answer 2

Rate = k[A]^m[B]^n where,

m and n = orders of reaction
k = rate constant

Question 3

Define order of reaction

Answer 3

An order of reaction is defined as the power to which the concentration of its reactant is raised in the rate equation

Question 4

How do you find order of reaction

Answer 4

1. If [A] changes and the rate stays the same, the order of reaction with respect to A is 0
2. If the rate is proportional to [A], then the order of reaction with respect to A is 1
3. If the rate is proportional to [A]^2, then the order of reaction with respect to A is 2

Question 5

How do you find orders of reaction

Answer 5

You can only find orders of reaction from experiments - they can’t be worked out from chemical equations

Question 6

What is k?

Answer 6

k is the rate constant - number that links the rate of reaction to the concentration of the reactants. The bigger the value of k, the faster the reaction

Question 7

Does k change for each reaction?

Answer 7

The rate constant is always the same for a certain reaction at a particular temperature

Question 8

What happens to the rate constant if you increase the temperature?

Answer 8

When you increase the temperature of a reaction, the rate of reaction increases - the number of collisions between the reactant molecules increases, and also the energy of each collision. But the concentrations of reactants and the orders of reaction stay the same. So the value of k must increase for the rate equation to balance