Chapter 8 - Reactivity Trends

Question 1

What is a reducing agent?

Answer 1

A species that donates it’s electrons to another species, thereby reducing that species.

Question 2

Which group are reducing agents commonly found?

Answer 2

Group 2

Question 3

What is the trend in reactivity down group 2?

Answer 3

Reactivity increases.

Question 4

Explain the trend of reactivity down group 2

Answer 4

Increased atomic radius and shielding effect so ionisation energies decrease. Therefore it’s easier to lose electrons.

Question 5

What are the products of a group 2 element reacting with water?

Answer 5

Metal hydroxide and hydrogen

Question 6

What is the product of a group 2 element reacting with oxygen?

Answer 6

Metal oxide

Question 7

What is the trend of solubility down group 2?

Answer 7

Increases

Question 8

Explain the trend of solubility down group 2

Answer 8

Down the group, the solution has a greater concentration of OH-.

Question 9

Given that group 2 oxides, hydroxides and carbonates neutralise acids, what can they be referred to as?

Answer 9

Bases

Question 10

Given that most group 2 oxides, hydroxides and carbonates are soluble in water, what are they also besides bases?

Answer 10

Alkalis

Question 11

What is the use of calcium hydroxide in agriculture?

Answer 11

Increases the pH of acidic soils.

Ca(OH)(2) + 2H+ -> Ca2+ + 2H(2)O

Question 12

How are group 2 compounds used in medicine?

Answer 12

Used in indigestion tablets as antacids, often a suspension of a metal hydroxide in water.

Question 13

What is another name for group 2?

Answer 13

Alkaline Earth Metals

Question 14

What is another name for group 7?

Answer 14

Halogens

Question 15

What is the trend in boiling point down group 7?

Answer 15

Increases

Question 16

Explain the trend in boiling point down group 7

Answer 16

More electrons,
Stronger London forces,
More energy to break intermolecular forces,
Boiling point increases.

Question 17

What is the trend in reactivity down group 7?

Answer 17

Reactivity decreases

Question 18

Explain the trend in reactivity down group 7

Answer 18

Atomic radius increases,
More inner shells,
Shielding increases,
Nuclear attraction decreases,
Reactivity decreases.

Question 19

What do more reactive halogens do to less reactive halide ions?

Answer 19

Displace them

Question 20

What can displacement reactions be used to identify?

Answer 20

Which halide is present in solution.

Question 21

Which compound is used to test for halides?

Answer 21

Silver nitrate solution

Question 22

How can the results for a halide test be further tested?

Answer 22

Solubility in ammonia solution

Question 23

What is disproportionation?

Answer 23

A redox reaction in which the same element is both oxidised and reduced.

Question 24

Describe the test for carbonates

Answer 24

Carbonates react with acids to form carbon dioxide gas.
Add dilute nitric acid to testing solution. If bubbles observed could be a carbonate. To prove its CO(2), bubble gas through lime water, a white precipitate will form.

Question 25

Describe the test for sulphates

Answer 25

Aqueous barium ions are added to the solution. If a white precipitate forms, there is a sulphate.

Question 26

In the halide tests, what happens to chloride with silver nitrate and then ammonia

Answer 26

Silver nitrate - white precipitate | Ammonia - soluble in dilute ammonia

Question 27

In the halide tests, what happens to bromide with silver nitrate and then ammonia

Answer 27

Silver nitrate - cream precipitate | Ammonia - soluble in concentrated ammonia

Question 28

In the halide tests, what happens to iodide with silver nitrate and then ammonia

Answer 28

Silver nitrate - yellow precipitate | Ammonia - insoluble in concentrated ammonia

Question 29

What is the correct order for these anion tests?

Answer 29

Carbonate test, sulphate test, halide test

Question 30

Why is this the correct order for anion tests carbonate, sulphate, halide?

Answer 30

Carbonates also form a white precipitate in the sulphate test but not vice versa. Carbonates and sulphates form precipitates with silver nitrate.

Question 31

Describe the test for ammonium ions

Answer 31

Add aqueous NaOH to the solution, Ammonia gas is produced, Can be detected with moist indicator paper as it will turn blue.