Rate Equations & Arrhenius

Question 1

How do you find the individual order of something eg A

Answer 1

Look where A changes and the other things stay the same. Then compare A with rate

Question 2

What’s the units for rate

Answer 2

Moldm^-3 s^-1

Question 3

What’s the units for [A] eg

Answer 3

Moldm^-3

Question 4

How do you know what species is the catalyst

Answer 4

it will be in the rate equation but not the overall equation

Question 5

What is 0 order

Answer 5

No effect on ROR

Question 6

What is 1st order

Answer 6

The same as ROR

Question 7

What is 2nd order

Answer 7

The ROR is the [conc] squared ^2

Question 8

How does temperature effect the rate constant (K)

Answer 8

As temperature increases the rate constant increases

Question 9

Define the rate constant (k)

Answer 9

a number that connects the concentration of reactants in a reaction to the rate of that reaction

Question 10

Define order of reaction

Answer 10

the power to which the concentration of that reactant is raised in the rate equation

Question 11

How do you work out activation energy (Ea) in the Arrhenius equation

Answer 11

1. RT(In A - In K)
2. Then divide by 1000

Question 12

How do you work out T in the Arrhenius equation

Answer 12

Activation energy/ R(In A - In k)

Question 13

In the Arrhenius equation what units must activation energy be in

Answer 13

Joules. So if in kJ then multiply by 1000 to get in J

Question 14

What will the units of A (Arrhenius constant) be the same as

Answer 14

The units of the rate constant

Question 15

How do you work out the Arrhenius constant

Answer 15

K divided by e to the power of (-Ea/RT)

Question 16

How would you know if iodine has all reacted

Answer 16

It would go from brown to colorless

Question 17

How do you work out the rate equation from 2 or more reaction mechanisms

Answer 17

rate equation for a reaction includes all reactants which appear before and during the slowest step (rate determining step) in the mechanism
Intermediates are ruled out

Question 18

How could you use a graph to work out Ea using R= 8.31

Answer 18

1. Work out gradient from graph
2. write down Gradient = -Ea/8.31
3. • Ea = 8.31 x gradient
4. Divide by 1000

Question 19

In what circumstance can the order of a reaction with respect or something be ignored?

Answer 19

• if there is a much larger amount of that than the other reactants
• the conc of it will stay almost constant

Question 20

How would you know from a graph that a reaction is zero order?

Answer 20

• if it is a straight line
• Say the gradient is constant
• So the rate of reaction does not change as the reactant is used up