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A-Level Chemistry - OCR > Chapter 8 - Reactivity Trends > Flashcards

Chapter 8 - Reactivity Trends Flashcards

Group 2, The halogens and Quantitative analysis.

1
Q

What is a reducing agent?

A

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

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2
Q

Which group are reducing agents commonly found?

A

Group 2

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3
Q

What is the trend in reactivity down group 2?

A

Reactivity increases.

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4
Q

Explain the trend of reactivity down group 2

A

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

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5
Q

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

A

Metal hydroxide and hydrogen

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6
Q

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

A

Metal oxide

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7
Q

What is the trend of solubility down group 2?

A

Increases

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8
Q

Explain the trend of solubility down group 2

A

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

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9
Q

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

A

Bases

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10
Q

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

A

Alkalis

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11
Q

What is the use of calcium hydroxide in agriculture?

A

Increases the pH of acidic soils.

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

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12
Q

How are group 2 compounds used in medicine?

A

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

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13
Q

What is another name for group 2?

A

Alkaline Earth Metals

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14
Q

What is another name for group 7?

A

Halogens

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15
Q

What is the trend in boiling point down group 7?

A

Increases

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16
Q

Explain the trend in boiling point down group 7

A

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

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17
Q

What is the trend in reactivity down group 7?

A

Reactivity decreases

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18
Q

Explain the trend in reactivity down group 7

A 
Atomic radius increases,
More inner shells,
Shielding increases,
Nuclear attraction decreases,
Reactivity increases
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19
Q

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

A

Displace them

20
Q

What can displacement reactions be used to identify?

A

Which halide is present in solution.

21
Q

Which compound is used to test for halides?

A

Silver nitrate solution

22
Q

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

A

Solubility in ammonia solution

23
Q

What is disproportionation?

A

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

24
Q

Describe the test for carbonates

A

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.

25
Q

Describe the test for sulphates

A

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

26
Q

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

A

Silver nitrate - white precipitate

Ammonia - soluble in dilute ammonia

27
Q

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

A

Silver nitrate - cream precipitate

Ammonia - soluble in concentrated ammonia

28
Q

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

A

Silver nitrate - yellow precipitate

Ammonia - insoluble in concentrated ammonia

29
Q

What is the correct order for these anion tests?

A

Carbonate test, sulphate test, halide test

30
Q

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

A

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.

31
Q

Describe the test for ammonium ions

A

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

32
Q

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

A

Run a displacement reaction

33
Q

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

A

Orange colour will form as the chlorine would have displaced the bromide ion

With cyclohexane - you will see a orange colour

34
Q

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

A

Brown colour change as the chlorine would have displaced the Iodine ion

In cyclohexane - it is violet colour

35
Q

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

A

Brown colour change as the halogen would have displaced the Iodine ion

In cyclohexane- it would be a violet colour change

36
Q

What colour is Cl2 in water

A

Pale green

37
Q

What colour is fluorine

A

Pale yellow

38
Q

Describe the astatine

A

Rare, radioactive and decays rapidly

Least reactive halogen

39
Q

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

A

Halogens

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

40
Q

What compound neutralises stomach acid

A

Magnesium hydroxide

Calcium carbonate

41
Q

At RTP describe chlorine, bromine and iodine

A

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

42
Q

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

A

Cl2(aq) + H20(l)&raquo_space;> HCLO(aq) + HCL(aq)

Disproportionation reaction

43
Q

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

A

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

44
Q

What do household bleach contain

A

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

45
Q

Benefits and risk of chlorine use

A

Disinfectant for water
Ensure no disease breakout

Respiratory irritant
Cause cancer b/ of the formation of chlorinated hydrocarbons

46
Q

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

A

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

A-Level Chemistry - OCR (35 decks)

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