Determining the Order - Rates of reaction (1.4)

Question 1

How do you determine the order?

Answer 1

• Plot a graph of initial rate vs concentration
• This gives different shapes for each order of reaction

0 order = flat horizontal line
1st order = straight line (directly proportional) from 0 (conc. & rate)
2nd order = exponential increase curve upwards from 0 (conc. & rate)

Question 2

How do you deduce rate equations?

Answer 2

Collect a small sample of selected experimental data, including the rate of reaction for multiple experiments

The experiments must be:

• The same reaction
• Carried out at the same temperature
• Vary the concentration of only one reagent each time

Question 3

Using initial rates, how do you determine that it is 1st order w/ respect to a reagent?

Answer 3

When the concentration of the reagent doubles (the other stays the same), the rate of reaction doubles

Question 4

Using initial rates, how do you determine that it is 2nd order w/ respect to a reagent?

Answer 4

When the concentration of the reagent doubles (the other stays the same), the rate of reaction quadruples

Question 5

What is ‘k’ in the rate equation?

Answer 5

The rate constant - it is a constant at a given temperature w/ a specified catalyst

Question 6

The units of the rate constant vary & depend on the overall order of the reaction. True or false?

Answer 6

True

Question 7

What factors affect the rate constant?

Answer 7

• Temperature

- Choice of catalyst

Question 8

Are solids included in the rate equation?

Answer 8

No

E.g If A+B -> C and B is a solid, the rate= [C]/[A]