Rates & Energy

Question 1

How can the rate of a reaction be found?

Answer 1

Measuring how much of a reactant is used

How much of a product is formed in the time taken

Question 2

Which 2 equations can calculate ROR?

Answer 2

Amount of reactant used/ time OR amount of product formed/ time

Question 3

What does the rate of reaction measure?

Answer 3

The speed of a reaction or how fast it is.

Question 4

How can you calculate the ROR from a graph?

Answer 4

Find the gradient at any given point; the steeper the gradient, the faster the reaction

Question 5

A reaction can only occur if …..?

Answer 5

Particles collide

Question 6

What is the activation energy?

Answer 6

The minimum energy that substances need to react

Question 7

What factors will increase the rate of reaction?

Answer 7

Factors which will increase the chance of collisions or increase the energy of the particles

Question 8

List the 5 factors that increase the ROR

Answer 8

Temperature
Concentration of solutions
Pressure of gases
Surface area of solids
Using a catalyst

Question 9

Why do powders react faster than solid large pieces?

Answer 9

Powders have a larger surface area so more of the surface is exposed to react and means there is more collisions in the same time so the powder reacts much faster

Question 10

Why does a higher temperature mean a faster reaction?

Answer 10

Increasing the temperature increases the speed of the particles in a reaction meaning they collide more often and a larger proportion will collide with greater energy than the activation energy which increases the rate of reaction

Question 11

By how much will the rate of reaction increase if the temperature is increased by 10 degrees?

Answer 11

Double the rate of reaction ps, twice as fast

Question 12

Why do freezer foods sty fresher for longer?

Answer 12

The decrease in temperature will increase the time that it takes for the reactions within the food to take place; decrease of 10 degrees reaction is twice as slow

Question 13

Why does a higher concentration increase the ROR?

Answer 13

A higher concentration means there are more particles dissolved in the same solution so the particles are closer together so will collide more frequently and more collisions go to succession

Question 14

Why does increasing the pressure increase the ROR?

Answer 14

Increasing the pressure puts more molecules in the same volume and so they collide more frequently this increases the ROR

Question 15

How do catalysts speed up the ROR?

Answer 15

They lower the activation energy.

Question 16

Why can catalysts be used again and again?

Answer 16

It is not used up so can be collected at the end of a reaction and reused

Question 17

Why do different reactions need different catalysts?

Answer 17

Catalysts often work with only one type of reaction

Question 18

What are the benefits of using catalysts in industrial processes?

Answer 18

The reduce the energy needed and the time needed and so reduce costs they may also reduce the fossil fuels need so conserves resources and reduces pollution

Question 19

What is bad about using transition metal catalysts?

Answer 19

Some of these metals and their compounds are toxic and may cause harm if the enter the environment

Question 20

What 2 areas of science offer possibilities for new or better catalysts?

Answer 20

Nanoscience and enzymes

Question 21

What is an exoteric reaction?

Answer 21

Reactions that transfer energy to the surroundings

Question 22

Exoteric reactions include:

Answer 22

Combustion, burning fuels
Oxidation, respiration
Neutralisation, reactions involving acids and bases

Question 23

What is an endothermic reaction?

Answer 23

Reactions that take energy in from the surroundings

Question 24

What usually happens in an exoteric reaction?

Answer 24

The temperature increases

Question 25

What are the 2 ways that show a reaction is endothermic?

Answer 25

Either it cools the surroundings or it needs to be heated to keep it going

Question 26

Give an example of an endothermic reaction and what makes it endothermic?

Answer 26

Thermal decomposition as it must be heated to keep the reaction going

Question 27

In reversible reactions the forward and reverse reactions involve ……… But ………. Energy transfers

Answer 27

Equal

Opposite

Question 28

A reversible reaction that is ……. In one direction must be …………. In another direction

Answer 28

Exothermic

Endothermic

Question 29

Why must blue copper sulphate be heated continuously to change it into anhydrous copper sulphate?

Answer 29

Endothermic reaction

Question 30

Why does adding water to anhydrous copper sulphate cause the mixture to get hot?

Answer 30

The reaction is exothermic

Question 31

Give an ad and a disad of a re-usable hand warmer compared with a single use hand warmer

Answer 31

Ad: less waste, less materials or resources used
Disad: has to be heated so it can be used again, slower reaction smaller temp rise

Question 32

Suggest an ad and disad of a chemical cold pack compared with an ice pack

Answer 32

Ads: can be used anywhere, can be stored easily,
Disad: only be used once, more waste, more possibly hazardous