The rate and extent of chemical change

Question 1

What is the rate of reaction?

Answer 1

The rate of a reaction is how fast the reactants are changed into products.

Question 2

Give two examples of slow reactions

Answer 2

Rusting of Iron

Chemical weathering

Question 3

Give one example of a moderate speed reaction

Answer 3

Magnesium metal reacting with an acid to produce a gentle stream of bubbles.

Question 4

Give one example of a fast reaction

Answer 4

Burning

Question 5

On a rate of reaction graph what does a line with a steep gradient mean?

Answer 5

The steeper the line the faster the reaction.

Question 6

On a rate of reaction graph what does a line with a shallow gradient mean?

Answer 6

The shallower the line the slower the reaction

Question 7

What do particles need in order to react?

Answer 7

Particles must collide with enough energy in order to react.

Question 8

How are reaction rates explained perfectly?

Answer 8

The collision theory

Question 9

What does a rate of reaction depend on?

Answer 9

• The collision frequency of reacting particles, more collisions = faster reaction
• Energy transferred during a collision, particles have to collide with enough energy for a collision to be successful.

Question 10

What is activation energy?

Answer 10

The minimum amount of energy that particles need to react.

Question 11

Why to particles need activation energy?

Answer 11

In order for the particles to have enough energy to break the bonds in the reactants and start the reaction.

Question 12

What will the increasing amount of particle collisions mean?

Answer 12

Increasing number of particle collisions = increase in rate of reaction.

Question 13

What four things does the rate of reaction depend on?

Answer 13

Temperature
Surface Area
The concentration of solution or pressure of gas
Presence of a catalyst

Question 14

How does increasing the temperature effect the rate of the reaction?

Answer 14

Increasing the temperature = increase the rate of reaction

Question 15

What happens to the particles when you increase the temperature of the reaction?

Answer 15

Increasing the temperature = particles all move faster = more energy = more successful collisions

Question 16

How does increasing the concentration or pressure effect the rate of reaction?

Answer 16

Increasing the concentration or pressure = increasing the rate of reaction

Question 17

What does a solution being more concentrated mean?

Answer 17

If a solution is more concentrated it means there are more particles in the same volume.

Question 18

What does a gas having more pressure mean?

Answer 18

When a gas has a higher pressure it means that there is the same number of particles but in a small;er space.

Question 19

What happens to the particles when you increase the concentration of the reaction?

Answer 19

There are more successful collisions because there are more particles in the same space so there is less space for the particles to spread out so they bang in to each other more frequently.

Question 20

What happens to the particles when you increase the pressure of the reaction?

Answer 20

When you increase the pressure there is less space for the particles to spread out so there are more successful collision because they bang into each other more frequently.

Question 21

How does increasing the surface area effect the rate of reaction?

Answer 21

Increasing the surface area = increasing the rate of the reaction.

Question 22

How do you increase a solids surface area to volume ratio?

Answer 22

By breaking the solid up into smaller pieces.

Question 23

What happens to the particles when you increase the surface area?

Answer 23

When you increase the surface area it means that for the same volume of the solid the particles around it have more area to work on- so there will be more successful collisions.

Question 24

How does using a catalyst effect the rate of reaction?

Answer 24

By using a catalyst it increases the rate of reaction.

Question 25

What is a catalyst?

Answer 25

A catalyst is a substance that speeds up a reaction without being used up in the reaction itself.

Question 26

What is the point of using a catalyst?

Answer 26

The catalyst is used to speed up a reaction by decreasing the activation energy needed for the reaction to occur. The offer an alternate pathway for the reaction with a lower activation energy.

Question 27

What is the equation for the rate of reaction?

Answer 27

Rate reaction = Amount of reactant used or amount of product formed / Time

Question 28

What are the three different ways you can measure the rate of reactions?

Answer 28

Precipitation and colour change Change in mass The volume of gas given off

Question 29

When is it appropriate to use precipitation or change in colour to measure the rate of the reaction?

Answer 29

It is appropriate when the initial solution is transparent and the product is a precipitate which clouds the solution.

Question 30

How do you measure the rate of reaction using precipitation and colour change?

Answer 30

You can observe a mark, that is under the flask, through the solution and measure how long it takes for it to disappear. The faster the mark disappears the quicker the reaction.

Question 31

How do you measure the rate of the reaction using precipitates and colour change if the reactants are coloured and the product is colourless or vise versa?

Answer 31

If the reactants are coloured and the products are colourless (or vice versa), you can time how long it takes for the solution to lose (or gain) its colour.

Question 32

What is a disadvantage of measuring the rate of reaction using precipitation or colour change?

Answer 32

The results are subjective, the times will differ depending on the person measuring the results.

Question 33

What is the advantage of measuring the rate of the reaction using precipitates and colour change?

Answer 33

You can plot a rate of reaction graph from the results.

Question 34

When measuring the rate of reaction using the change in mass, how do you measure the speed of a reaction that produce a gas?

Answer 34

Measuring the speed of a reaction that produces a gas can be carried out using a mass balance.

Question 35

When measuring the rate of reaction using the change in mass, how does it work?

Answer 35

A flask filled with the solution you are measuring with pieces of metal, that the solution will react with to create the gas, this is plugged with a cotton ball and is sat on measuring scales and you record the beginning mass. As the solution reacts with the metal gas is given off and decreasing the mass of solution. Time and record at regular intervals. The faster the drop in mass the faster the rate of reaction.

Question 36

What are the two advantages of measuring the rate of reaction using the change in mass?

Answer 36

It is the most accurate method of measuring the rate of reaction You can plot it on a rate of reaction graph

Question 37

What is the disadvantage of measuring the rate of reaction using the change in mass?

Answer 37

There is a chance of the gas being released straight into the room instead of staying in the flask.

Question 38

What does measuring the rate of reaction using the volume of the gas given off involve?

Answer 38

This method involves using a gas syringe to measure the volume of the gas given off.

Question 39

How does the rate of reaction using the volume of gas given off work?

Answer 39

You have a flask with the solution in it as well as metal pieces with a bung on top, to stop the gas from escaping, it has a gap for the tube that attaches to the syringe. The more gas given off during the given time interval the faster the reaction. Plot at regular intervals.

Question 40

What is the advantage of measuring the rate of reaction using the volume of gas given off?

Answer 40

You can plot a rate of reaction graph

Question 41

What is the disadvantage of measuring the rate of reaction using the volume of gas given off?

Answer 41

If the reaction is to vigorous you can easily blow the plunger out the end of the syringe and it will destroy all the results of the experiment.