3.1.9.1 Rate Equations

Question 1

What is the rate of reaction?

Answer 1

The change in concentration over time

Question 2

What is the rate of a reaction at any instant?

Answer 2

Draw a tangent and measure y / x on a concentration time graph

Question 3

What is the inital rate?

Answer 3

The rate of reaction when t = 0

Question 4

What is the rate expression?

Answer 4

Rate = k [X]' [Y]'
k = rate constant
[X] = concentration of X
[Y] = concentration of Y
' = order of the reactant

Question 5

What does the k stand for in the rate expression?

Answer 5

The rate constant
It is different for every reaction and varies with temperature
If all the species are 1M, the rate equation is equal to the value of k

Question 6

How do you work out the overall order of the reaction?

Answer 6

Add the orders of each species

Question 7

How does the order of a species relate to the change in rate?

Answer 7

Zero order: change in concentration does not affect the rate
1st order: doubled concentration doubles the rate, tripled concentration triples the rate
2nd order: doubled concentration quadruples the rate, tripled concentration multiplies the rate by 9

Question 8

What are the units for the rate constant?

Answer 8

mol dm s

Powers depend on putting the units in the expression