Orders of reactions

Question 1

What is the order of reaction?

Answer 1

The power to which the concentration is raised to in the rate law expression

Question 2

What is the overall order of a reaction?

Answer 2

The sum of the individual co-efficients

Question 3

What would be the rate law equation with A in first order?

Answer 3

v = k[A]

Question 4

What is a zero order reaction?

Answer 4

The rate is independent of the reactant concentrations

Does not vary with varying concentrations of reactant

Question 5

What is the rate of reaction equal to when the reactants are zero order?

Answer 5

Rate constant

Question 6

What are the units for k for v = k[A] ?

Answer 6

v / [A]
M s-1 / M
= s-1

Question 7

What are the two ways a second order reaction can be written?

Answer 7

v = k [A] 
v = k [A][B]

Question 8

What is always the denominator when you work out the units of k for second order reaction?

Answer 8

M²

Question 9

What are the units for k for a second order reaction?

Answer 9

M-1 S-1

Question 10

Do chemical reactions always have to have an integer order?

Answer 10

No

eg. it could be 1/2

Question 11

What are the two methods for working out rate law?

Answer 11

Method of isolation

Method of initial rates

Question 12

What is the method of isolation to work out the rate law?

Answer 12

Set up the experiment so only one component changes, eg. A and the other 2 remain constant
This allows you to measure the order of reaction with respect to A

Question 13

What is the method of initial rates to work out the rate law?

Answer 13

Assume the first portion of the concentration vs time plot is linear
To work out the initial rate, use the equation Change in conc / change in time
Then you can use the initial rate to work out the orders of the reactant

Question 14

How is the order of a reaction determined?

Answer 14

Experimentally

Question 15

How is the molecularity of a reaction determined?

Answer 15

It is only a theoretical concept

Question 16

How is the order of a reaction obtained?

Answer 16

From the rate of the overall reaction

Question 17

How can the molecularity of a reaction be deduced?

Answer 17

it is deduced from the rate determining step in the proposed reaction mechanism

Question 18

What type of values can the order of reaction have?

Answer 18

May have a whole number, zero or even fractional value

Question 19

What type of values can molecularity of a reaction have?

Answer 19

Always a whole number and never zero

Question 20

How can the order of a reaction not be obtained?

Answer 20

Not obtained from a balanced of stochiometric reaction

Question 21

How can the molecularity of a reaction be obtained?

Answer 21

from the balanced equation of a single reaction step from a known mechanism

Question 22

What does the order of reaction not tell you?

Answer 22

Doesn’t give you any information about the reaction mechanism, though it gives some suggestions

Question 23

What does the molecularity of a reaction tell you?

Answer 23

reveals some fundamental facts about the reaction mechanism

Question 24

is the order of a reaction able to be changed?

Answer 24

Yes

Is magnitude can change when the reaction conditions are altered

Question 25

Does the molecularity of the reaction change when the reaction conditions are altered?

Answer 25

No

Question 26

What is the general equation for the method of isolation?

Answer 26

v = k[A]α [B]β [C]ˣ

Question 27

What is the general equation for the initial rates method?

Answer 27

α = log v1/v2 / log [A]1/[A]2

Question 28

Units for zero order?

Answer 28

M s⁻¹

Question 29

Units for first order?

Answer 29

s⁻¹

Question 30

Units for second order?

Answer 30

M⁻¹ s⁻¹