Unit 4

Question 1

What is the formula for the overall rate of reaction

Answer 1

R = change in concentration/change in time

Question 2

What is the unit for rate

Answer 2

mol dm^-3 s^-1

Question 3

What are the ways to measure rate of reaction

Answer 3

Titration
Colorimetry
Change in volume of gas
Electrical conductivity
Pressure

Question 4

What do rate equations show

Answer 4

The mathematical relationship between rate and concentration

Question 5

What is the relation between rate and concentration

Answer 5

They are directly proportional to each other

Question 6

What does k represent

Answer 6

k is the rate constant

Question 7

When is k a constant

Answer 7

At a specific temperature

Question 8

How can rate equations be found

Answer 8

Rate equations can only be determined and cannot be found theoretically

Question 9

What are the units of k in a zero order reaction

Answer 9

mol dm^-3 s^-1

Question 10

What are the units of k in first order reaction

Answer 10

s^-1

Question 11

What are the units of k in a second order reaction

Answer 11

mol^-1 dm^3 s^-1

Question 12

What is the rate determining step

Answer 12

The slowest step in a multistep reaction mechanism

Question 13

Determining rate order from a graph

Answer 13

There are two ways of determining rate order from a graph
1. Continuous method
2. Initial rate method

Question 14

What is the continuous method

Answer 14

One reaction mixture where samples are taken at regular intervals the sample is quenched and the concentration of a reactant or product is found by titration, to generate data to enable concentration-time or volume-time graphs to be plotted.

Question 15

What are the steps to find rate order using the continuous method

Answer 15

1. Draw a concentration time graph
2. Find the half-life of the reaction at different concentrations

Question 16

What is half-life

Answer 16

The time taken for the concentration of a reactant to fall to its original value

Question 17

When half-life is constant…

Answer 17

The reaction is first order with respect to the reactant

Question 18

If half-life doubles as the reaction proceeds then…

Answer 18

The reaction is second order with respect to that reactant

Question 19

Half-life decreases for…

Answer 19

A zero order reaction

Question 20

What is the exam answer for half-life

Answer 20

The half life is almost constant. Each half life is _____ seconds apart

Question 21

What is the initial rates method

Answer 21

Several runs of the experiment are carried out, changing the concentration of one reagent. The time taken for a certain amount of product to be produced.

Question 22

How to find rate at which product is produced from initial rate method

Answer 22

Rate = 1/T

Question 23

What is the graph that is plotted for the initial rates method

Answer 23

Rate at which the product is formed against the concentration

Question 24

What does a zero order reaction look like on the initial rates method graph

Answer 24

A straight line parallel to the x axis

Question 25

What does a first order reaction look like on the initial rates method graph

Answer 25

A straight line going through the origin

Question 26

What does a second order reaction look like on the initial rates method graph

Answer 26

A curved line going through the origin and increasing

Question 27

when is titration used

Question 28

when is colorimetry used

Question 29

when is change in mass used

Question 30

how is change in volume of gas measured

Answer 30

using a gas syringe or collecting it over water

Question 31

when is electrical conductivity used

Question 32

when is pressure used and how is it measured

Answer 32

nanometer

Question 33

what is the formula for the acid-catalysed iodination of propanone?

Answer 33

CH₃COCH₃ + I₂ + (H^+(catalyst)) → CH₃COCH₂I + 2(H^+) + (I^-)

Question 34

what is the rate equation of the acid-catalysed iodination of propanone?

Answer 34

Rate = k[CH₃COCH₃][H^+]