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 increases

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 such as barium carbonate but not vice versa. So first must rule out there isn’t any carbonates present Carbonates and sulphates form precipitates with silver nitrate. Such as Ag2CO3 and Ag2SO4.

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.

Question 32

If I want to work out which halide is present in a solution what can I do

Answer 32

Run a displacement reaction

Question 33

A Cl2 is added to a Br- ion. What observation will you see with and without the polar solvent cyclohexane present

Answer 33

Orange colour will form as the chlorine would have displaced the bromide ion With cyclohexane - you will see a orange colour

Question 34

A Cl2 is added to a I- ion. What observation will you see

Answer 34

Brown colour change as the chlorine would have displaced the Iodine ion In cyclohexane - it is violet colour

Question 35

A Br2 is added to a I- ion. What observation will you see

Answer 35

Brown colour change as the halogen would have displaced the Iodine ion In cyclohexane- it would be a violet colour change

Question 36

What colour is Cl2 in water

Answer 36

Pale green

Question 37

What colour is fluorine

Answer 37

Pale yellow

Question 38

Describe the astatine

Answer 38

Rare, radioactive and decays rapidly | Least reactive halogen

Question 39

What groups are the best oxidising event and describe the oxidising trend as you go down the group

Answer 39

Halogens As you go down the group the halogens become weaker oxidising agents

Question 40

What compound neutralises stomach acid

Answer 40

Magnesium hydroxide | Calcium carbonate

Question 41

At RTP describe chlorine, bromine and iodine

Answer 41

Chlorine is a pale green gas Bromine liquid is extremely toxic, and vaporises readily arises RTP. Iodine is a solid with grey-black crystals

Question 42

Show the reaction of chlorine with water and what kind of reaction is this

Answer 42

Cl2(aq) + H20(l) >>> HCLO(aq) + HCL(aq) Disproportionation reaction

Question 43

Show the reaction of chlorine with cold, dilute aqueous sodium hydroxide and what kind of reaction is this

Answer 43

Cl2(aq) + 2NaOH(aq) >>> NaCLO(aq) + NaCl(aq) + H20(l)

Question 44

What do household bleach contain

Answer 44

Sodium chlorate (I), NaCLO made by reacting chlorine with sodium hydroxide

Question 45

Benefits and risk of chlorine use

Answer 45

Disinfectant for water Ensure no disease breakout Respiratory irritant Cause cancer b/ of the formation of chlorinated hydrocarbons

Question 46

Explain the test that would be carried out on a mixture of ions

Answer 46

Carbonate test: If you see bubbles, continue adding dilute nitric acid until the effervescence stops All carbonate ion will then have been removed and there will be none left to react in the next tests. We don’t use sulfuric acid or hydrochloric acid because it contains sulfate and chloride ions , which will show Up in the sulfate and halide test Sulfate test: Add an excess of Ba(NO3)2 Any sulfate ion present will precipitate out as barium sulfate Filter the solution to remove the barium sulfate Halide test: Any carbonate or sulfate ion present have already been removed. Therefore any PPT must involve halide ions. Add NH3 to confirm which halide you have