Chapter 8 - Reactivity trends Flashcards

1
Q

What is another name for group 2 ?

A

Alkaline earth metals

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2
Q

What is a reducing agent ?

A
  • A species that donates its electrons to another species, thereby reducing that species
  • It is known as an electron donor
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3
Q

Which group are reducing agents commonly found ?

A

Group 2

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4
Q

What is the trend in reactivity down group 2 ?

A

Reactivity increases as you go down group 2

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5
Q

Explain why reactivity increases as you go down group 2

A
  • As you go down the group the atomic radius and shielding effect increase so ionisation energies decrease
  • Therefore it is easier to lose electrons and they get more reactive down the group
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6
Q

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

A

Metal hydroxide and hydrogen

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7
Q

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

A

Metal oxide

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8
Q

What is the trend of solubility like down group 2 ?

A

Solubility increases as you go down the group

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9
Q

Explain why solubility increases as you go down group 2

A

As you go down the group the solution has a greater concentration of hydroxide ions

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10
Q

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

A

Bases

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11
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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12
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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13
Q

How are group 2 compounds used in medicine ?

A
  • Used as antacids in indigestion tablets
  • They are often a suspension of a metal hydroxide in water
  • Milk of magnesia is an example of this
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14
Q

What is the trend in boiling point down group 7 ?

A

The boiling point down the group increases

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15
Q

Explain why the boiling point increases down group 7

A
  • There are more electrons as you go down the group
  • Therefore stronger london forces are present
  • More energy is required to break these intermolecular forces
  • Therefore the boiling point increases down the group
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16
Q

What is the trend in reactivity down group 7 ?

A

Down the group the reactivity decreases

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17
Q

Explain why reactivity decreases as you go down group 7

A
  • The atomic radius increases
  • More inner shells so there is a greater shielding effect
  • Nuclear attraction therefore decreases and it is harder to gain an electron
  • This leads to reactivity decreasing down the groups

You have to remember that group 7 elements need to gain an electron, not lose one

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18
Q

What do more reactive halogens do to less reactive halogens ?

A

More reactive halogens displace less reactive halogen ions

19
Q

What can chlorine displace ?

A

Iodine and bromine

20
Q

What can bromine displace ?

A

Iodine only

21
Q

What can iodine displace ?

A

It can’t displace chlorine or bromine

22
Q

What can displacement reactions be used to identify ?

A

It allows you to identify which halide is present in the solution

23
Q

Which compound is used to test for halides ?

A

Silver nitrate solution, AgNO3

24
Q

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

A

For solubility in ammonia solution

25
Q

What is disproportionation ?

A

It is a redox reaction in which the same element is both oxidised and reduced

26
Q

Describe the test for carbonates

A
  • Carbonates react with acids to form carbon dioxide gas
  • Add dilute nitric acid (HNO3) to the testing solution
  • If bubbles are observed a carbonate could be present
  • To prove it is carbon dioxide, bubble it through lime water, a white precipitate will be formed
27
Q

Describe the test for sulphates

A
  • Aqueous barium ions are added to the solution.
  • If a white precipitate forms, there is a sulphate.
  • This is because barium sulphate BaSO4 is formed
28
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

29
Q

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

A
  • Silver nitrate - cream precipitate

- Ammonia - soluble in concentrated ammonia

30
Q

In halide tests, what happens to iodine with silver nitrate and then ammonia ?

A
  • Silver nitrate - yellow precipitate

- Ammonia - insoluble in concentrated ammonia

31
Q

What is the correct order for the anion tests ?

A
  • Carbonate test
  • Sulphate test
  • Halide test
32
Q

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

A
  • Carbonates also form a white precipitate in the sulphate test but not vice versa.
  • Carbonates and sulphates form precipitates with silver nitrate
33
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, the indicator paper will turn blue
34
Q

What colour is chlorine in water ?

A

Pale green

35
Q

What colour is bromine in water ?

A

Orange

36
Q

What colour is iodine in water ?

A

Brown

37
Q

What colour is chlorine in cyclohexane ?

A

Pale green

38
Q

What colours is bromine in cyclohexane ?

A

Orange

39
Q

What colour is iodine in cyclohexane ?

A

Violet

40
Q

Describe the test for halides

A
  • Add aqueous silver nitrate (AgNO3) to an aqueous solution or halide
  • A silver halide precipitate will be formed
  • Add aqueous ammonia to test the solubility of the precipitate
41
Q

What is the ionic equation for testing for ammonium ions ?

A

NH4+ + OH- —> NH3 + H2O

42
Q

What is the ionic equation for testing for halide ions ?

A

Ag + + X- —> AgX

43
Q

What is the ionic equation for testing for sulphate ions ?

A

Ba + + SO42- —> Ba2SO4