3.1.9 - Rate equations

Question 1

What is the generalised rate equation for reaction ‘‘aA + bB →’’?

Answer 1

r = k[A]^m[B]^n

Question 2

What is the unit for rate of reaction?

Answer 2

r is used as symbol for rate
The unit of r is usually mol/dm^3/s

Question 3

In the rate equation, what do ‘m’ and ‘n’ represent?
-What numbers can they be?
-What does this mean?
-How are they worked out?

Answer 3

m, n are called reaction orders. Orders are usually integers 0,1,2

0 means the reaction is zero order with respect to that reactant
1 means first order
2 means second order

NOTE: the orders are not the same as the stoichiometric coefficients in the balanced equation. They are worked out experimentally.

Question 4

Recall what each order tells us about the relationship between concentration of A and the rate of reaction

Answer 4

ON GOOGLE DOCS

Question 5

How do we work out total order?

Answer 5

add all the individual orders together (m+n+…)

Question 6

How do we work out the units of the rate constant (k)?

Answer 6

must be worked out from the rate equation similar to Kc

Common:
For a 1st order overall reaction the unit of k is s^-1
For a 2nd order overall reaction the unit of k is mol/dm^3/s
For a 3rd order overall the unit of k is mol^2/dm^6/s

Question 7

What is important to note about k the rate constant, regarding temperature?

Answer 7

-k is only constant at a fixed temperature
-the value of k refers to a specific temperature and it increases if we increase temperature

Question 8

The value of k is independent of

Answer 8

The value of k is independent of {{c1::concentration and time}}