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A Level Chemistry > Module 3: Chapter 8 - Reactivity Trends > Flashcards

Module 3: Chapter 8 - Reactivity Trends Flashcards

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1
Q

How does 1st Ionisation energy change down group 2?

A

It decerases as both the atomic radius and electron shielding increases causing a weaker attraction from nucleus to electron in the outer shell. Therefore there is a lower ionisation energy down the group

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2
Q

How does melting point change down group 2?

A

Melting point decreases as there is weaker metallic bonding. There is the same number of delocalised valence electrons, however the metal ions are larger causing weaker attraction between the positive metal ions and delocalised valence electrons. Therefore lower melting points. There is a change in trend after Mg due to a change in the way ions pack together

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3
Q

How does atomic radius change down group 2?

A

Atomic radius increases down the group due to more electron shells

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4
Q

What is the observation of Magnesium with water?

A
  • Very slow reaction with cold water
  • Reaction with steam - burns witha. white flame to form white powder
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5
Q

What is the observation of Calcium with water?

A

effervesence in water and forms a white solid

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6
Q

What is the observation of Strontium with water?

A

Vigorous effercesence in water forming a colourless solution

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7
Q

What is the observation of Barium with water?

A

Extremely vigrorous effervesence in water forming a colourless solution

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8
Q

What is the observation of berrylium with water?

A

No reaction

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9
Q

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

A
  • Cold water: Mg + 2H₂O -> Mg(OH)₂ + H₂
  • Steam: Mg + H₂O -> MgO + H₂
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10
Q

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

A

Ca + 2H₂O -> Ca(OH)₂ + H₂

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11
Q

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

A

Sr + 2H₂O -> Sr(OH)₂ + H₂

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12
Q

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

A

Ba + 2H₂O -> Ba(OH)₂ + H₂

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13
Q

What is the trend in reactivity of group 2?

A

increases down the group

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14
Q

Why are group 2 metals reducing agents?

A

They can lose electrons, donating them to other species

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15
Q

Why do group 2 metals become more reactive down the group?

A

As you travel down group 2, both the first and second ionisation energies decrease causing reactivity to increase. This is because there is a greater atomic radius and greater electron shielding causing the nuclear attraction on the valence electrons to decrease

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16
Q

How is ionisation energy proportional to reactivity?

A

Inversly proportional, the lower the ionisation energy, the higher the reactivity

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17
Q

What is the most common type of reaction of a group 2 element and why?

A

Redox, each group 2 element contains 2 electrons in the outer s sub-shell meaning each metal ion can be easily oxidised, losing 2 electrons to form a 2+ ion.

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18
Q

What is the reaction of group 2 elements with oxygen?

A

Group 2 elements react with oxygen to form a metal oxide

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19
Q

What is the reaction of magnesium with oxygen?

A

2Mg + O₂ -> 2MgO

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20
Q

What are the observations of the reaction of magneisum with oxygen?

A

The magnsium burns with a brilliant white light forming a white powder

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21
Q

What is the reaction of a group 2 metal with a dilute acid?

A

Metal + acid -> salt + hydrogen

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22
Q

What is the reaction of group 2 oxides with water?

A

The oxides of group 2 elements react with water, releasing hydroxide ions, forming a solution of the metal hydroxide. As the group 2 hydroxides are only slightly soluble in water, when the solution becomes saturated any further metal and hydroxide ions form a solid precipitate

Metal oxide + water -> Metal hydroxide

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23
Q

What is the reaction of calcium oxide with water?

A

CaO(s) + H₂O(l) -> Ca(OH)₂(s)

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24
Q

What is the solubility of group 2 hydroxides?

A

The solubility of group 2 hydroxides increases down the group

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25
Q

Why does Mg(OH)₂(aq) have a pH of ∼10 but Ba(OH)₂(aq) have a pH of ∼13?

A

Mg(OH)₂ is only very slightly soluble in water. The solution has a low OH- concentration and therefore a pH of only 10, whereas Ba(OH)₂ is much more soluble in water, the solution has a greater OH- concentration and therefore a higher pH of 13

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26
Q

How are group 2 compounds used in agriculture?

A

Group 2 oxides, hydroxides, and carbonates have many uses related to their basic properties. For example, calcium hydroxide is added to fields to increase the pH of acidic soils, the calcium hydroxide neutralises acids in the soil forming neutral water

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27
Q

How are group 2 compounds used in medicine?

A

Group 2 compounds are often used to treat acid indigestion. Many indigestion tablets use magnesium and calcium carbonate or alternatively a solution of magnesium hydroxide. These basic tablets/solutions neutralise the hydrochloric acid in your stomach, forming harmless salt and water in the process

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28
Q

What is milk of magnesia?

A

Milk of magnesia is a suspension of magnesium hydroxide in water (suspension not solution as magnesium hydroxide is only very slightly soluble in water)

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29
Q

What are the full and ionic equations for the displacement reaction of Cl₂(g) with KBr(aq)

A
  • Cl₂(g) + 2KBr(aq) -> 2KCl(aq) + Br₂ (aq)
  • Cl₂(g) + 2Br⁻(aq) -> Br₂(aq) + 2Cl⁻(aq)
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30
Q

What are the full and ionic equations for the displacement reaction of Cl₂(g) with MgI₂(aq)

A
  • Cl₂(g) + MgI₂(aq) -> MgCl₂(aq) + I₂(aq)
  • Cl₂(g) + 2I⁻(aq) -> I₂(aq) + 2Cl⁻(aq)
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31
Q

What is the trend in boiling points of the halogens?

A

Boiling point increases down the group

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32
Q

Explain why boiling point increases as you go down the halogens

A

As you go down the group the atoms contain more electrons, therefore there are more London forces between molecules. As a result more energy is required to break the intermolecualr forces causing boiling points to increase

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33
Q

What is the appearance and state of Fluorine at RTP?

A

pale yellow gas

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34
Q

What is the appearance and state of Chlorine at RTP?

A

Pale green gas

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35
Q

What is the appearance and state of Bromine at RTP?

A

Red-brown liquid

36
Q

What is the appearance and state of Iodine at RTP?

A

Shiny grey-black solid

37
Q

What is the appearance and state of Astatine at RTP?

A

Never been seen

38
Q

What is the same between all halogen molecules?

A

They are all diatomic

39
Q

What is the electronic arrangement of the outershell of a halogen?

A

s2p5

40
Q

What is the electronic arrangement of the outershell of a group 2 metal?

A

s2

41
Q

Why are halogens good oxidising agents?

A

Halogens contain 7 valence electrons meaning they only need to gain 1 electron to form a 1- halide ion with the same electronic configuration as the nearest noble gas. Therefore other species can easily lose electrons to halogen atoms, reducing halogen whilst being oxidised in the process. Therefore halogens are good oxidising agents

42
Q

What colour is chlorine solution in water?

A

Pale green

43
Q

What colour is bromine solution in water?

A

Orange

44
Q

What colour is iodine solution in water?

A

Brown

45
Q

What colour is Chlorine solution in cyclohexane?

A

Pale Green

46
Q

What colour is Bromine solution in cyclohexane?

A

Orange

47
Q

What colour is iodine solution in cyclohexane?

A

Violet

48
Q

How does reactivity change down the halogens?

A

It decreases down the group

49
Q

Why may cyclohexane solution be used to identify the halide ions?

A

An aqueous solution of bromine and iodine are hard to differentiate between, therefore cyclohexane may be used to clearly see the different colours

50
Q

What is the observation when you add chlorine solution to an aqueous solution of bromide ions?

A

The solution would turn orange from Br₂ formation

51
Q

What is the observation when you add chlorine solution to an aqueous solution of Iodide ions?

A

The solution would turn brown/violet from I₂ formation

52
Q

What is the observation when you add Bromine solution to an aqueous solution of Chloride ions?

A

No reaction

53
Q

What is the observation when you add Bromine solution to an aqueous solution of Iodide ions?

A

The solution would turn Violet/brown from I₂ formation

54
Q

What is the observation when you add Iodine solution to an aqueous solution of Chloride ions?

A

No Reaction

55
Q

What is the observation when you add Iodine solution to an aqueous solution of Bromide ions?

A

No Reaction

56
Q

What is the Ionic equation when Chlorine solution is added to an aqueous solution of bromide ions?

A

Cl₂(aq) + 2Br⁻(aq) -> 2Cl⁻(aq) + Br₂(aq)

57
Q

What is the Ionic equation when Chlorine solution is added to an aqueous solution of Iodide ions?

A

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

58
Q

What is the Ionic equation when Bromine solution is added to an aqueous solution of Iodide ions?

A

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

59
Q

What type of reaction is a displacement reaction?

A

A redox reaction

60
Q

Explain the trend in reactivity of the halogens:

A

As you travel down the halogens, the atomic radius increases and there are more inner shells so shielding increases. As a result there is less nuclear attraction to capture an electron from another species. As a result reactivity decreases down the group

61
Q

What is the strongest oxidising agent?

A

Fluorine

62
Q

Why is fluorine the strongest oxidising agent?

A

It is the most reactive element, allowing it to gain electrons from other species more readily than other halogens. Therefore halogens become weaker oxidisng agents down the group

63
Q

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

A

Disproportionation reaction

64
Q

What type of reaction is the reaction of chlroine with cold dilute sodium hydroxide?

A

Disproportionation reaction

65
Q

What is the reaction chlorine with water?

A

Cl₂(aq) + H₂O(l) -> HClO(aq) + HCl(aq)

(chlorine is both oxidised and reduced)

66
Q

How does adding chlorine to water kill bacteria?

A

When chlorine is added to water, they react, forming HClO (Chloric(I) acid) and hydrochloric acid. The bacteria are killed by the HClO and the chlorate(I) ions, ClO⁻, rather than by the chlorine itself.

67
Q

What is the reaction of chlorine with cold, dilute aqueous sodium hydroxide?

A

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

(Chlorine is both oxidised and reduced)

68
Q

What does household bleach contain?

A

NaClO(aq) (Sodium Chlorate(I))

69
Q

What are the benefits of using chlorine in drinking water?

A

Chlorine ensures that drinking water is fit to drink and that bacteria are killed, preventing outbreaks of diseases such as cholera and typhoid

70
Q

What are the risks of using chlorine in drinking water?

A
  • Chlorine gas is extremely toxic, in small doses it is a respiratory irritant and in larger doses can be fatal
  • Chlorine in drinking water can react with organic hydrocarbons, the product of which is suspected to be carcinogenic
71
Q

What is the ionic equation of the reaction of a halide ion with an aqueous silver ion?

A

Ag⁺(aq) + X⁻(aq) -> AgX(s)

72
Q

What is qualitative analysis?

A

Analysis which relies on simple observations rather than measurements

73
Q

What is the test for a carbonate ion?

A
  1. In a test tube, add dilute nitric acid to the solid or solution to be tested
  2. If you see effervescence, the unknown compound could be a carbonate
  3. Bubble this gas through aqeous calcium hydroxide (limewater), if a fine white precipitate is formed (calcium carbonate), there is carboante present
74
Q

What is the reaction of sodium carbonate solution with dilute nitric acid?

A
75
Q

What is the solubility of sulfates?

A

Most sulfates are soluble in water, however barium sulfate (BaSO₄) is extremely insoluble

76
Q

What is the test for sulfate ions?

A
  1. Add barium nitrate solution to the test tube
  2. If a white precipitate forms, sulfate is present
77
Q

Why is barium nitrate used instead of barium chloride in the test for sulfate ions?

A

The test for sulfate ions is often used preceding a halide test, if barium chloride is used, this is introducing chloride ions to the solution.

78
Q

What is the halide test?

A
  1. Add aqueous silver nitrate to and aqueous solution of a halide
  2. The silver halide precipitates are different colours - silver chloride is white, silver bromide is cream coloured, and silver iodide is yellow
  3. As the precipitates may be hard to distinguish between, add aqueous ammonia to test the solubility of the precipitate - silver chloride is soluble in dilute ammonia solution, silver bromide is soluble in concentrated ammonia solution, and silver iodide is insoluble in ammonia solution
79
Q

What colour are the silver halide precipitates?

A
  • Silver chloride - white
  • Silver Bromide - cream
  • Silver Iodide - yellow
80
Q

What is the solubility of silver halide precipitates in ammonia solution?

A
  • Silver chloride - soluble in dilute ammonia solution
  • Silver bromide - soluble in concentrated ammonia solution
  • Silver iodide - insoluble in ammonia solution
81
Q

What is the sequence of tests for anions?

A
  1. Carbonate test
  2. Sulfate test
  3. halide test
82
Q

Why is the carbonate test carried out first in the sequence of anion tests?

A

The carboante test is done first as neither sulfate nor halide ions produce bubbles with dilute acid, therefore the carboante test can be carried out immediately without the possibility of an incorrect conclusion

83
Q

Why is the sulfate test carried out second in the sequence of anion tests?

A

Barium carbonate is a white precipitate in water, therefore you must carry out the carbonate test before the sulfate test or a false positive may be produced. You must only carry out the sulfate test once you know that there are no carbonates present

84
Q

Why is the halide test carried out last in the sequence of anion tests?

A

Both silver carbonate and silver sulfate produce precipitates in water, therefore a halide test can only be carried out once you know that there are no sulfate or carbonate ions otherwise a false positive result may occur.

85
Q

What is the test for ammonium ions?

A
  1. Add aqueous sodium hydroxide to the solution
  2. If ammonium ions are present, ammonia gas will be produced, however it is extremely soluble in water and therefore no bubbles will be produced
  3. Warm the mixture in a warm water bath to release the ammonia gas
  4. Test the gas produced with damp red litmus paper, if ammonia gas is present the litmus paper will turn blue, indicating a positive result for the ammonium ions
86
Q

What must you do if a solution contains a mixture of ions for a qualitative analysis test?

A
  1. When testing for carbonate, continue to add dilute nitric acid until the bubbling stops. This means that all carboante ions will have been removed
  2. When testing for sulfate, add excess barium nitrate solutoon to ensure any sulfate ions will precipitate out as barium sulfate, then you must filter the solution to remove the barium sulfate precipitate
  3. Carry out halide test as normal
87
Q

What are antacids?

A

medicines used to treat acid indigestion

A Level Chemistry (31 decks)

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