Rate and extent of chemical change

Question 1

What are the two equations for rate of reaction?

Answer 1

Quantity of reactant used / time taken

Or

Quantity of product formed / time taken

Question 2

How does measuring change in mass help us find rate of reaction?

Answer 2

Using a flask with your object and solution.

Putting it on a scale.

Gas escapes so the mass decreases.

Use a timer and see how the mass has changed between that time.

Use the equation for rate of reaction (Quant of mass used / time taken)

Question 3

What is the unit used for measuring change in mass / time.

Answer 3

Grams per second

Question 4

To measure the volume of a gas formed in a reaction, when might you choose to use a gas syringe rather than a measuring cylinder?

Answer 4

To measure a soluble gas

Question 5

How do you find rate of reaction using the volume of the gas produced practical?

Answer 5

Using a flask and a upside down cylindrical flask filled with water,

Putting a tube from the flask and the the cylindrical flask.

The reaction is happening in the flask releasing gases.

The gases displace the water and pushes the water down and then you measure the volume of the gas that has displaced the water.

Do this with a timer and use the formula for rate of reaction.

Question 6

How do you find the rate of reaction using colour change?

Answer 6

Using a flask with a cross at the base and your solid and solution.

Using a precipitate (solid formed), putting it in your solution and time how long it takes for the cross to not able to be seen

Use the formula 1 / time.

Question 7

What does it mean when the line is flat on a rate graph?

Answer 7

Reaction has stopped

Question 8

What does having a steeper gradient show in a rate graph?

Answer 8

It has a higher rate of reaction.

Question 9

How do you calculate rate of reaction at a specific time?

Answer 9

Draw a tangent and calculate the gradient

Question 10

On a rate graph showing product formed over time, what causes the gradient to eventually flatten out?

Answer 10

The reactant has been used up

Question 11

Use your knowledge of particles to explain why the rate of the reaction decreased.

Answer 11

Less particles in a given volume (1)

Particles less likely to collide (1)

With enough energy or less successful collisions (1)

Question 12

What is pressure?

Answer 12

Pressure is a measurement of the number of particles in a given volume of gas.

Question 13

How does temperature affect rate of reaction?

Answer 13

Higher temperature = Higher rate of reaction

More energy towards the particles meaning more collisions.

Question 14

How does pressure / concentration affect rate of reaction?

Answer 14

Higher pressure / concentration = higher rate of reaction

As more particles, more collisions.

Question 15

Why does having a larger surface area increase rate of reaction?

Answer 15

This is because there are more particles exposed to the other reactant.

Greater chance of particles colliding.

Question 16

What is a catalyst?

Answer 16

A substance that speeds up a chemical reaction without being used up.

Question 17

How does a catalyst work?

Answer 17

It reduces the activation energy of the reaction.

Question 18

Are catalysts chemically changed by a reaction?

Answer 18

No they are chemically unchanged by a reaction.

Question 19

Why are catalysts useful for producing chemicals in industry?

Answer 19

Catalysts are used in industry because they lower the activation energy required, thereby making reactions more efficient and cost effective.

Question 20

What is the collision theory?

Answer 20

Collision theory states that chemical reactions can only occur when reacting particles collide and have sufficient energy.

Question 21

What is activation energy?

Answer 21

The minimum amount of energy that particles must have to react is called activation energy.

Question 22

What is a reversible reaction?

Answer 22

A reversible reaction is one in which the products of the reaction can react to produce the original reactants again.

Question 23

If you heat up NH4Cl to make NH3 + HCl how do reverse the reaction?

Answer 23

By cooling it down. (ENDOTHERMIC)

Question 24

If you heat up hydrated copper sulphate it turns into anhydrous copper sulphate. How do you reverse the reaction?

Answer 24

Adding water

Question 25

What is a equilibrium?

Answer 25

It is when the forward and reverse reactions occur at exactly the same rate.

Question 26

Why is equilibrium only occur in a closed system?

Answer 26

No reactant can be released or added so the reactions can happen at the same time.

Question 27

When a reversible reaction reaches equilibrium are the concentrations of all reactants equal?

Answer 27

No as there may be more reactants products than reactants.

Question 28

What is name of the type of reaction that takes in heat energy?

Answer 28

Endothermic.

Question 29

Describe the energy change when an excess of water is added to the anhydrous white copper sulfate.

Answer 29

Energy is transferred to the surroundings or energy is transferred from
the anhydrous copper sulphate to the surroundings or heat energy/heat is given off. [1]
The reaction is exothermic. [1]

Question 30

What is Le Chatelier’s principle?

Answer 30

If a change is made to an equilibrium. The equilibrium will act to oppose the change.

Example: If temperature increases, the endothermic reaction will happen more and cools down the system.

Question 31

In the reaction A + B ⇌ C + D, what happens to the amounts of the reactants and products if the concentration of D is increased in equilibrium?

Answer 31

A and B increase; C and D decrease