Rates, equilibrium and pH

Question 1

Define the rate of reaction

Answer 1

the change in concentrations of a reactant or a product per unit time

Question 2

Define the rate constant

Answer 2

this is the constant that links the rate of reaction with the concentrations of the reactants raised to the powers of their orders in the rate equation

Question 3

Write the rate of reaction equation

Answer 3

change in concentration of reactant or product/ time

Question 4

Describe zero order

Answer 4

if the order is 0 with respect to reactant A then the rate [a]^0

• the rate is unaffected by changing concentration of A
• any number to the power 0 is equal to one

Question 5

Describe first order

Answer 5

if the order is 1 with respect to reactant B then the rate [B]^1

• rate is directly proportional to concentration
• if [B] increases by 2 times the rate also increases by 2 times

Question 6

Describe second order

Answer 6

if the order is 2 with respect to C then the rate is [C]^2
- the change in rate will be equal to the concentration squared
For example
- if [C] increases by 2 times, the rate increases by 4 times
- if [C] increases by 3 times the rate increases by 9 times

Question 7

Write out a rate equation with letters

Answer 7

WRITE IT NOW

Question 8

Does a zero order appear in the rate equation

Answer 8

A 0 order will not appear in the rate equation as it does not affect the rate of reaction

Question 9

Do you show the power of 1 in the equation

Answer 9

NO

Question 10

How do you work out the overall order

Answer 10

An overall order is the sum of individual orders

Question 11

Write down the units of rate constants

Answer 11

Zero order - moldm-3s-1
First order - s-1
Second order - dm3mol-1s-1
Third order - dm6mol-2s-1

Question 12

What do you measure in reactions involving acids or bases

Answer 12

• pH changes by carrying out titrations

- pH changes by using a pH meter

Question 13

What do you measure in reactions involving gases

Answer 13

• change in volume or pressure

- loss in mass of reactants

Question 14

What do you measure in reactions that produce visual changes that we observe

Answer 14

• formation of a precipitate

- colour change

Question 15

How do you work out the rate using a graph

Answer 15

rate = change in concentration/ time taken for change to take place

Question 16

What is a half life

Answer 16

this is the time taken for concentration of a reactant to decrease by half

Question 17

Write the symbol for half life

Answer 17

• WRITE IT

Question 18

Draw the concentration - time graph for zero order reactions

Answer 18

DRAW IT

Question 19

Draw the concentration-time graph for first order reactions

Answer 19

DRAW IT

Question 20

Write the equation that uses the half life to find the rate constant

Answer 20

k= ln2/ half life

Question 21

How do you work out t=o (initial rate)

Answer 21

find the gradient of the tangent at 0

Question 22

How do you use the initial rate to determine the order to reactions

Answer 22

• To determine the order of reaction vary the concentrations of the reactant several times and obtain the initial rate each time then plot the results on a graph to determine the order

Question 23

The time taken for the visible event to occur is …

Answer 23

inversely proportional to the initial rate, the shorter the time taken for change the faster the reaction is
1/t

Question 24

DRAW THE RATE-CONCENTRATION GRAPH FOR ZERO ORDER

Answer 24

DRAW IT

Question 25

DRAW THE RATE-CONCENTRATION GRAPH FOR FIRST ORDER

Answer 25

DRAW IT

Question 26

DRAW THE RATE-CONCENTRATION GRAPH FOR SECOND ORDER

Answer 26

DRAW IT