3.1.9 Rate equations

Question 1

What is the rate equation?

Answer 1

Rate= k[A]^m[B]^n
Where m and n are the orders of the reaction with respects to the reactants.

Question 2

Which factors affect the value of k, the rate constant?

Answer 2

Temperature, they are directly proportional.

Question 3

What is Arrhenius equation?

Answer 3

k = Ae^-(Ea/RT)
Where A is the Arrhenius constant, this varies between different reactions.

Question 4

What is the rate determining step?

Answer 4

The slowest step in a multistep reaction.

Question 5

What are the continuous methods for monitoring rate?

Answer 5

Calorimetry
Gas volume
Gas mass

Question 6

What are the methods for measuring the initial rate of a fixed concentration change?

Answer 6

Disappearing cross
Iodine clock

Question 7

Describe the method for a continuous method for monitoring rates.

Answer 7

Have an excess of other reactants.
Monitor the change in [] of the reactant you’re interested in.
Plot a graph for [] vs time
Determine the order with respect to the reactant.
Calculate the rate using the gradient

Question 8

Describe the method for an initial rate method for monitoring rates.

Answer 8

Fix the [] of all the reactants except 1 and double this and determine the initial rate.
Then compare the impact of changing [] to change in rate, to determine order.
Repeat with the other reactants.
OR
Repeat 3 times for different []
Plot rate vs [] to determine order

Question 9

When determining order with respect to a reactant, why do we add other reactants in excess?

Answer 9

So that they don’t affect rate.
The concentrations of other reaction remains almost constant (as the change is negligible.)
So, it essentially becomes 0 order with respect to other reactants.