Rates of Reactions

Question 1

Give an example of a slow rate of reaction:

Answer 1

oxidisation (rusting)

Question 2

Give an example of a medium rate of reaction:

Answer 2

Baking (cakes, cookies etc.)

Question 3

Give an example of a very fast rate of reaction:

Answer 3

Explosions (e.g. fireworks)

Question 4

What are the two ways we can measure rates of reaction?

Answer 4

1) Measure the rate at which the reactant is used up.

2) Measure the rate at which a product is formed (i.e. volume of gas made/time taken)

Question 5

In this equation, which parts are the reactants and which part is the product?

HCl (aq) + Mg (s)&raquo_space;> Mgcl2 (aq) + H2 (g)

Answer 5

HCI (aq) + Mg (s) = REACTANTS

MCl2 (aq) + H2 (g) = PRODUCTS

Question 6

What is the equation for rate of reactant?

Answer 6

Volume formed / Time in seconds

Question 7

How do you calculate the MEAN rate of reaction

Answer 7

Quantity of product formed / Time in seconds

Question 8

convert these into measurements of time:

1 cm3/s
2 cm3/s
4 cm3/s

Answer 8

1 minute
30 seconds
15 seconds

Question 9

What can the rate of reaction tell us?

Answer 9

How fast reactants turn into products.

Question 10

There are lots of reactions taking place in the human body and it is important for them to work at the correct rates. Why?

Answer 10

They happen at the correct rate to supply our cells with what they need, whenever required.

Question 11

How can you measure the rate of reaction using decreasing mass of a reaction mixture?

Answer 11

You can measure the rate at which the mass of a reaction mixture changes if the reaction gives of a gas. You can measure and record the mass at regular time intervals.

Question 12

How can you measure the rate of reaction using the increasing volume of gas given off?

Answer 12

If a reaction produces a gas, you can use the gas to find out the rate of reaction. You do this by collecting the gas and measuring the volume given off at time intervals.

Question 13

How can you measure the rate of reaction using the decreasing light passing through a solution?

Answer 13

Some reactions in solutions make a suspension of an insoluble solid (precipitate). This makes the solution go cloudy. You can use this to measure the rate at which the precipitate appears.

Question 14

What must happen for a chemical reaction to occur?

Answer 14

The reactant particles must collide

Question 15

What does the rate of reaction depend on?

Answer 15

The rate of successful collisions between reactant particles. (the more successful collisions there are, the faster the rate of reaction)

Question 16

Things that affect the rate of reaction

Answer 16

• Temperature
• Concentration of reactants in solution
• Pressure of gaseous reactants
• Surface area
• Adding a catalyst

Question 17

How does temperature affect rate of reaction?

Answer 17

The higher the temperature, the more energy the particles have meaning they can move around more thus allowing them to collide more often which leads to a faster reaction.

Question 18

How does concentration affect rate of reaction?

Answer 18

The more concentrated the solution (the more particles there are), the greater the chance of collisions with other reactants leading to a faster reaction.

Question 19

How does surface area affect rate of reaction?

Answer 19

Any reaction involving a solid can only take place at the surface of a solid. If the solid is split into several pieces, the surface area increases which leads to more successful collisions

Question 20

How does a catalyst affect the rate of reaction

Answer 20

A catalyst substance speeds up a reaction but is chemically unchanged at the end of the reaction. They only change the rate of reaction and not the product.

Question 21

How do you work out the:

• Area of a square/rectangle?
• Area of a cube?
• Volume of a cube?

Answer 21

1) Width * height
2) Length * width * 6
3) length * width * depth

Question 22

Calculate the surface area of A cube with the side length of 4cm:

Answer 22

96cm2

Question 23

Calculate the volume of a cube with a side

length of 4 cm:

Answer 23

64cm3

Question 24

What does Aq mean?

Answer 24

Aqueous (In solution)

Question 25

What is pressure?

Answer 25

The number of gas particles given in a certain area.

Question 26

How can we change pressure?

Answer 26

We can change pressure by changing the amount of particles in a gas as well as the size of a given area.

Question 27

Why are catalysts beneficial?

Answer 27

• Catalysts reduce activation energy which makes them cheaper.
• Catalysts remain unchanged at the end of a chemical reaction
• Good for making ethanol and it produces Carbon Dioxide not monoxide which is better

Question 28

What is dynamic equilibrium?

Answer 28

It occurs In a reversible reaction when the forward and backward reactions are going at the same rate.

Question 29

What is homogenous?

Answer 29

All the reactants are in the same group- same state of matter.

Question 30

What is Le Chatelier’s principle?

Answer 30

If dynamic equilibrium is disturbed by changing the conditions or oppose the change