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OCR Chemistry A-level > Chapter 8-Group 2, The Halogens and Quantative Analysis > Flashcards

Chapter 8-Group 2, The Halogens and Quantative Analysis Flashcards

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1
Q

What is th common name given to group 2 metals?

A

Alkaline earth mentals

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2
Q

What is the trend in reactivity down group 2?

A

Reactivity increases down the group

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3
Q

What are three physical properties of group 2 metals?

A
  • High melting and boiling points
  • Low density metals
  • Form colourless/white compoiunds
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4
Q

The highest energy electrons of group 2 metals are in which subsell?

A

S subshell

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5
Q

Why does reactivity increases down group 2?

A

The atoms in group 2 elements react by losing 2 electrons. Going down electrons are lost more easily due to the increase in shielding and atomic radius

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6
Q

What is the trend in the first ionisation energy going down group 2?

A

The first ionisation energy decreases because

  • atomic radius increases
  • nuclear attraction decreases
  • shielding increases
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7
Q

What type of reaction is the reaction between group 2 elements and oxygen?

A

REDOX

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8
Q

What are the two products when group 2 elements react with water?

A

Hydroxide and hydrogen gas

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9
Q

Which group 2 element doesnt react with water?

A

Beryllium

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10
Q

What type of reaction is the reaction between a group 2 element and water?

A

REDOX

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11
Q

What is oxidised and what is reduced in a reaction between a group 2 element and water?

A

The metal is oxidised

One hydrogen atom from each water is reduced

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12
Q

What are the products when a group 2 element reacts with a dilute acid?

A

Salt and hydrogen gas

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13
Q

Write an equation for the reaction of calcium and hydrochloric acid

A

Ca (s) + 2HCl (aq) —> CaCl2 (s) +H2 (g)

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14
Q

What is formed when group 2 oxides react with water?

A

Metal hydroxide

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15
Q

Write an equation for the reaction between a group 2 oxide and water

A

MO (s) + H2O —> M(OH)2 (aq)

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16
Q

Which group 2 metal oxide is insoluble in water?

A

Beryllium oxide

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17
Q

What is the trend in hydroxide solubility down group 2?

A

Increases going down the group
Mg(OH)2 is slightly soluble
Be(OH)2 creates a strong alkaline solution

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18
Q

What is Ca(OH)2 used for? Include an equation

A

Its used to neutralise soil

Ca(OH)2 (aq) + 2HCl (aq) —> 2H2O (l) + CaCl2 (aq)

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19
Q

What is Mg(OH)2 used for?

A

Milk of magnesia is an antiacid used to treatt indigestion, heartburn etc.
This may be due to it slight solubility

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20
Q

What is calcium carbonate used for?

A

Found in limestone and marble which is used in the building industry

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21
Q

What is the drawback of using calcium carbonate in construstion? Include and equation

A

Group 2 carbonates react with acid

CaCO3 (s) + 2HCl (aq) —> CaCl2 (aq) + H2O (l) + CO2 (g)

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22
Q

What is the trend in melting point going down group 2 ? Why?

A

DECREASES

Due to ionic radius increasing and the electrostatic attraction between the nuclei and delocalised electrons decreasing

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23
Q

What is barium sulphate used for?

A

Used as barium meals for Xrays of the stomach and digestive system. This occurs because the barium atoms are heavy and good at absorbing Xrays. It can occur safely because barium has a poor solubility

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24
Q

What is the use of barium chloride?

A

Used to test for sulphate ions
1. Add an acid to remove any carbonate ions
2. Add barium chloride
If any sulphate ions are present a white ppt will form

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25
Q

List 2 properties of the halogens

A
  • low melting and boiling points

- exist as diatomic molecules

26
Q

What is the trend in boiling point going down group 7? Why?

A

As you go down group 7 molecules have more elctrons.
This menas that going down, london forces become stronger which are harder to break, so more energy is required.

Therefore boiling point INCREASES going down group 7

27
Q

What is the trend in reactivity going down group 7? Why?

A

Reactivity DECREASES because,

Atomic radius increases
Electrons shielding increases
Nuclear attraction decreases
Electron affinity decreases

28
Q

What is the trend in oxidising ability doing down gorup 7? Why?

A

Oxidising ability DECREASES

This is because Cl has the fewest occupied electron shells, the greatest force of attaction between the outer electrons and nucleus and therefore it is easiest to gain electrons and be reduced.

Oxidising agent-take an electron from a substance that has been oxidised

29
Q

What is the trend in reducing ability going down group 7? Why?

A

Reducing ability INCREASES going down

This is because I- has the most occupied electron shells, so the outer electrons are further from the nucleus, there is a weaker force of attraction between the nucleus and outer electrons. Therefore it is the easiest to be oxidised and lose electrons- bets reducing agent

30
Q

What is the colour of chlorine in water?

A

Pale green

31
Q

What is the colour of bromine in water?

A

Orange

32
Q

What is the colour of iodine in water?

A

Brown

33
Q

What is the colour of chlorine in cyclohexane?

A

Pale green

34
Q

What is the colour of bromine in cyclohexane?

A

Orange

35
Q

What is the colour of iodine in cyclohexane?

A

Violet

36
Q

Out of the three halides Cl-, Br- and I- which one can be oxidied by chlorine?

A

Br- and I- ions

37
Q

Write the equation ofr chlorine oxidising bromide ions

A

Cl2 (aq) + 2I- (aq) —> 2Cl- (aq) + I2 (aq)

38
Q

Out of the three halides Cl-, Br- and I- which one can be oxidised by bromine?

A

I- ions

39
Q

Write the equation for bromine oxidising iodide ions

A

Br2 (aq) + 2I- (aq) —> 2Br- (aq) + I2 (aq)

40
Q

Out of the three halides Cl-, Br- and I- which one can be oxidised by iodine?

A

None

41
Q

Define disproportionation

A

The oxidation and reduction of the same elment in a redox reaction

42
Q

What is the equation for the reaction of chlorine with water?

A

Cl2 (g) + H2O (l) —> HClO (aq) + HCl (aq)

43
Q

What type of reaction is the reaction of chlorine with water?

A

Disproportionation

Chlorine is both oxidised and reduced simultaneously

44
Q

Why is chlorine added to drinking water?

A

To kill the bacteria in the water (remove waterborne diseases) to make it safer to drink

45
Q

What are the two forms of the chlorate ion?

A

ClO- is chlorate (I)

ClO3- is chlorate (V)

46
Q

What is the equation for forming bleach?

A

Cl2 (aq) + 2NaOH (aq) —> NaCl (aq) + NaClO (aq) + H2O (l)

NaClO is bleach

47
Q

What are the objections to chlrine being added to water?

A
  • Chlorine is toxic when in excess

- Chlorine can react with hydrocarbons to form chlorinated hydrocarbons, some of which are carcinogens

48
Q

What are anions also known as?

A

Negative ions

49
Q

How can you test for carbonate ions?

A
  1. Add strong acid to the sample
  2. Collect the gas produced
  3. Pass through lime water

If positive fizzing will occur and lime water will turn cloudy

50
Q

Write an equation for the carbonate test

A

CO ₃ 2- (aq) + 2H+ (aq) —> H ₂O (aq) +CO ₂ (g)

51
Q

How can you test for sulphate ions?

A
  1. Add dilute hydrochloric acid
  2. Add barium chloride

If positive a white ppt will form

52
Q

Write an equation for the sulphate test

A

Ba2+ (aq) + SO ₄2- (aq) —> BaSO ₄ (s)

53
Q

What do you use to test for halide ions?

A

Acidified Silver nitrate, AgNO ₃

54
Q

Why do you add HNO ₃ to test for halide ions and not HCl?

A

The HNO ₃ removes carbonate ions.

Adding HCL would add Cl- ions which would give a false positive result

55
Q

How can you test for halide ions?

A
  1. Dissolve the sample in water
  2. Add aqueous silver nitrate
  3. Record the colour change
  4. If difficukt to distinguish the colour, add aqueous ammonia, first dilute ammonia then conc. ammonia
  5. Note the solubility of the precipitate
56
Q

Write the result and equation for Cl- test

A

White precipitate, soluble in dilute aqueous ammonia

Ag+ (aq) + Cl- (aq) —> AgCl (s)

57
Q

Write the result and equation for Br- test

A

Cream ppt, soluble in conc. aqueous ammonia only

Ag+ (aq) + Br- (aq) —> AgBr (s)

58
Q

Write the result and equation for I- test

A

Yellow ppt, insoluble in conc. and dilute aqueous ammonia

Ag+ (aq) + I- (aq) —> AgI (s)

59
Q

When testing for carbonate, sulphate and halide ions, which order should these tests be carried out and why?

A
  1. Carbonate test
  2. Sulphate test
  3. Halide test

They are tested in this order because barium ions form insoluble ppt of BaCO ₃ and silver ions form insoluble ppt of AgSo ₄

60
Q

What are cations also known as?

A

Positive ions

61
Q

How can you test for ammonium ions?

A
  1. Add sodium hydroxide to the same and warm gently
  2. Test the gas produced with red litmus paper

If positive the red litmus paper will turn blue and the ammonia will produce a pungent smell

62
Q

Write the equation for the ammonium test

A

NH ₄+ (aq) + OH- (aq) —> NH ₃ (aq) + H ₂O (l)

OCR Chemistry A-level (1 decks)

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