Chemical Industry 4: Order & Rate Equations

Question 1

Definition of order of a reaction

Answer 1

How much the concentration of a reactant effects the rate

Question 2

How is order shown in the rate equation

Answer 2

Power to which the concentration of the reactant is raised in the rate equation

Question 3

What are 3 orders

Answer 3

• 0 order
• 1st order
• 2nd order

Question 4

Explain the effect of 0 order

Answer 4

• rate is proportional to [ A ]^0 = 1

- Rate is not affected by changes in [ A ] = rate remains the same

Question 5

What do [ ] stand for

Answer 5

Concentration of in moldm^-3

Question 6

Explain the effect of 1st order

Answer 6

• Rate is proportional to [ A ] or [A]^1
• whatever you do to [A ] you do the same to rate

Eg. [ A ] x2 = rate x2

Question 7

Explain the effect of 2nd order

Answer 7

• Rate is proportional to [A]^2
• whatever you do to [A ] you square it and apply to rate

Eg. [ A ] x2 = rate x2^2 = rate x4

Question 8

What are the units of rate

Answer 8

Moldm^-3 s^-1

concentration / time

Question 9

Write expression of reaction rate equation for xA + yB —> products

Answer 9

Reaction rate = k [A]^m [ B ]^n

( k = (proportionality) rate constant & m/n = order number )

Note m/n are nothing to do with x/y

Question 10

How can orders of reaction be found

Answer 10

Can only be found experimentally can not be found by looking at original chemical equation

Question 11

What is the rule for catalysts and rate equations

Answer 11

Although catalyst not in chemical equation can still appear in rate equation

Question 12

What is k

Answer 12

Rate constant for a reaction = different for different reactions

Question 13

What is the only thing that effects k

Answer 13

Temperature

• k increase with temperature

( usually in experimental data given temperature would have remained constant )

Question 14

How do you work out the units of k

Answer 14

• Rearrange rate equation
• use order of reactions of different concentrations

LOOK IN NOTES

Question 15

What is the overall order of reaction

Answer 15

Sum of powers of the concentration terms in the rate equation

Question 16

Be able to deduce rate equation from table of experimental data

Answer 16

Look at notes

Question 17

What does a rate ( Y ) against concentration ( X) graph look like for 0 order

Answer 17

Horizontal line, —

Question 18

What does a rate ( Y ) against concentration ( X) graph look like for 1st order

Answer 18

Rising straight line, /

Question 19

What does a rate ( Y ) against concentration ( X) graph look like for 2nd order

Answer 19

Upwards curve

Question 20

What 2 methods can used to produce experimental data for rate-concentration graphs

Answer 20

1. INITIAL RATES METHOD = Doing several experiments where initial rate is measured & initial concentration of reagent is changed
2. CONTINUOUS RATES METHOD = doing 1 experiment where the rate and concentration of a reagent is measured at several times during that one reaction

Question 21

How can an iodine clock reaction be monitored

Answer 21

Progress of reaction can be measured by following the colour of iodine produced using starch = colourless —> blue-black complex