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AQA A Level Chemistry > Year 12- Periodicity (Inorganic Chemistry) > Flashcards

Year 12- Periodicity (Inorganic Chemistry) Flashcards

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1
Q

How does atomic radius change across a period and why?

A
  • Decreases from left to right
  • Increased number of protons creating stronger positive charge attracting electrons that are in the same shell with similar shielding
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2
Q

How does 1st ionisation energy change across a period?

A
  • Generally increases, except there’s a drop between Mg+Al and P+S
  • The general increase is due to increasing number of protons as the electrons are being added to the same shell
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3
Q

Why is there a small drop in 1st ionisation energy across a period from Mg to Al?

A

Mg has its outer electrons in the 3s subshell whereas Al is starting to fill the 3p subshell. Al’s electron is slightly easier to remove as the 3p electrons are higher in energy.

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4
Q

Why is there a small drop in 1st ionisation energy across a period from P and S?

A

Sulfur’s outer electron is being paired up with another electron. This pairing causes repulsion between the 2 electrons which makes the second one easier to remove.

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5
Q

How does the melting point change across period 1? - Na to Al

A

There is metallic bonding- it gets stronger the more electrons there are in the outer shell and sea of electrons.
A smaller ion with a greater positive charge also makes bonds stronger.

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6
Q

How does the melting point change across period 1?- Si

A

It is macromolecular. Many strong covalent bonds between atoms, high energy needed to break covalent bonds. It has the highest melting point.

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7
Q

How does the melting point change across period 1?- Cl2, S8 and P4

A

Simple molecular- weak VDW between molecules so little energy needed to break them. Low mps and bps.

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8
Q

How does the melting point change across period 1?-Ar

A

Monoatomic- weak VDWs between atoms. Lowest energy of all of them in the period.

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9
Q

Why does S8 have a higher mp than P4?

A

It has more electrons so has stronger VDWs between molecules.

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10
Q

How does atomic radius change down a group?

A
  • Increases down a group

- Atoms get more shells of electrons, more shielding, which makes the atom bigger

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11
Q

How does melting point change down a group?

A
  • Decreases down a group
  • Metallic bonding of groups 1 and 2 weakens as the atomic size increases. Distance between positive ions and delocalised electron increases so the electrostatic attraction weakens
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12
Q

How does 1st ionisation energy change down a group?

A
  • Decreases down a group

- Outermost electrons held more weakly as they get further from the nucleus due to increased shielding.

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13
Q

Does the reactivity of group 2 metals increase or decrease down a group?

A

Increases

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14
Q

Magnesium reaction with oxygen- equation and observations

A
  • 2Mg + O2 —> 2MgO
  • Burns with a bright white flame
  • Forms white solid with high melting point due to ionic bonding
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15
Q

Magnesium slow reaction with oxygen- equation and observations

A
  • 2Mg + O2 —> 2MgO

- Mg ribbon will often have a thin layer of MgO on it formed

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16
Q

How is a thin layer of MgO cleaned off Mg ribbon before a reaction?

A
  • By emery paper

- This is done to prevent a false result as both Mg and MgO will react but at different rates

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17
Q

Reaction of Mg with steam- equation and observations

A

-Mg (s) + H2O (g) –> MgO (s) + H2
(g)
-Produces MgO and Hydrogen
-Mg will burn with a bright white flame

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18
Q

Reaction of Mg with warm water- equation and observations

A
  • Mg + 2 H2O –> Mg(OH)2 + H2
  • Produces magnesium hydroxide and hydrogen
  • Slower reaction than with steam and there is no flame
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19
Q

How do group 2 elements react with cold water?- Equations and observations

A

-Ca + 2 H2O (l)–> Ca(OH)2
(aq) + H2
(g)
-Increasing vigour down the group
-Produces hydroxides
-Observations: fizzing, metal dissolving, solution heating up, less precipitate forms down the group

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20
Q

What precipitate does calcium make in a reaction with cold water?

A

white

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21
Q

How is titanium a useful metal?

A

It is abundant, has a low density and is corrosion resistant so is used for making strong, light alloys in aircraft.

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22
Q

Why isn’t titanium extracted with carbon?

A

Titanium carbide is formed instead

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23
Q

Why isn’t titanium extracted by electrolysis?

A

It has to be very pure

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24
Q

Steps in extraction titanium with magnesium

A

1) TiO2 (solid) is converted to TiCl4 (liquid) at 900*C
- TiO2 + 2 Cl2 + 2 C –> TiCl4 + 2 C

2) TiCl4 is purified by fractional distillation in an argon atmosphere
3) Ti is extracted by Mg in an argon atmosphere at 500*C
- TiCl4 + 2Mg –> Ti + 2 Mg

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25
Q

Why is titanium expensive?

A
  • The expensive cost of Mg
  • Batch process makes it expensive because the process is slower and requires more labour and energy is lost when reactor is cooled down after stopping
  • Due to argon and need for moisture (TiCl4 is susceptible to hydrolysis)
  • High temps in both stages
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26
Q

What is the trend of the solubility of Group 2 hydroxides down the group?

A

It increases

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27
Q

What is magnesium hydroxide classifies as in water?

A

Insoluble

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28
Q

What is calcium hydroxide classified as in water?

A

Partially soluble

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29
Q

What is magnesium hydroxide used as? Explain how and why.

A
  • Milk of magnesia used in medicine to neutralise excess stomach acid and treat constipation
  • Safe to use as it is weakly alkaline.
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30
Q

Why is it preferable to use calcium carbonate in medicine than magnesium hydroxide?

A

It doesn’t produce carbon dioxide gas.

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31
Q

What is calcium hydroxide used in?

A
  • When a white precipitate, it is used in agriculture to neutralise acidic soils
  • When aqueous solution, it is called lime water and is used to test for carbon dioxide. It turns cloudy as white calcium carbonate is formed.

Ca(OH)2 (aq) + CO2 (g) –> CaCO3 (s) + H2O (l)

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32
Q

What is solubility of barium hydroxide in water?

A

Very soluble

33
Q

What is the trend of solubility of Group 2 sulfates down the group?

A

It decreases- BaSO4 is least soluble

34
Q

Where is BaSO4 used?

A

In medicine- as a ‘Barium meal’ given to patients who need x-rays of their intestines. Ba absorbs x-rays so the git shows up on the image.
-Although barium compounds are toxic, it is safe due to its insolubility in blood.

35
Q

Why does barium metal react slowly with sulfuric acid?

A

The insoluble BaSO4 produced covers the surface of the metal and acts as a barrier to further attack.

  • Same effect happens with a lesser extent with metals going up the group as solubility increases
  • Doesn’t react the same with HCl and HNO3 as they form group 2 salts
36
Q

What is the test for sulfate ions?

A

]BaCl2 solution with HCl is added to a solution that contains sulfate ions to form a white precipitate of barium sulfate ions
Ba2+ (aq) + SO4 2-(aq) –> BaSO4(aq)

37
Q

Why is HCl used in test for sulfate ions and not H2SO4?

A
  • It is used as it reacts with carbonate impurities which are found in salts and form a white precipitate of BaCO3 (false result)
  • H2SO4 not used as it contains sulfate ions, giving a false positive result
38
Q

Fluorine properties

A
  • Very pale yellow gas

- Highly reactive

39
Q

Chlorine properties

A
  • Greenish, reactive gas

- Poisonous in high concentrations

40
Q

Bromine properties

A
  • Red liquid

- Gives off dense brown/orange poisonous flames

41
Q

Iodine properties

A

-Shiny grey solid sublimes to purple gas

42
Q

Trend in mp and bp down group 7

A

Increases down the group as molecules get larger with more electrons, increasing the strength of VDWs. This requires more energy to be overcome.

43
Q

Trend in electronegativity down group 7

A

It decreases going down the group as the atomic radius increases due to increasing shielding. The nucleus is therefore less able to attract the bonding pair of electrons.

44
Q

What is electronegativity?

A

The relative tendency of an atom in a molecule to attract electrons in a covalent bond to itself

45
Q

Trend in oxidising strength down the group

A

Decreases

46
Q

Displacement reactions of halide ions by halogens- reason

A

A halogen with a strong oxidising agent displaces a halogen that has a lower oxidising power from one of its compounds.

47
Q

Colours of solutions of halogens- displacement reactions with halide ions

A
  • Chlorine: very pale green solution (often clear)
  • Bromine: yellow solution
  • Iodine: brown solution (sometimes black solid)
48
Q

Reactions of halide ions with silver nitrate- procedure

A
  • Solution is made acidic with nitric acid: reacts with carbonates to prevent formation of precipitate Ag2CO3.
  • Then silver nitrate solution is added dropwise
49
Q

Reactions of halide ions with silver nitrate- how is a silver halides treated to differentiate colours that are similar?

A

With ammonia
-Silver chloride dissolves in dil. ammonia to form:
AgCl(s) + 2NH3(aq) –>[Ag(NH3)2]+(aq) + Cl- (aq)
-Silver bromide forms a similar ion reacting in conc. ammonia
-Silver iodide doesn’t react as it is too insoluble

50
Q

Observations of halide ions reaction with silver nitrate- colours

A
  • Fluorides: no precipitate
  • Chlorides: white precipitate
  • Bromides: cream precipitate
  • Iodides: pale yellow precipiates
    e. g. Ag+ (aq) +I- (aq) –> AgI (s)
51
Q

Trends of reducing ability going down the group

A

It increases- ions get bigger so its easier to give away outer electrons as the attraction to the nucleus is weaker

52
Q

Reactions of halide ions with conc. H2SO4- Fluoride and chloride

A

-Not strong enough to reduce the S in H2SO4 so no redox reactions occur, only acid-base ones.
1)F:
NaF(s) + H2SO4
(l) –>NaHSO4
(s) + HF(g)
Observations: White steamy fumes of HF are evolved.
2)Cl: similar reaction
Observations: White steamy fumes of HCl are evolved.

53
Q

Reactions of halide ions with conc. H2SO4- Bromide ions

A
  • Stronger reducing agents than CL- and F-
  • After the initial acid-base reaction, sulfur is reduced in H2SO4 from +6 to +4 in SO2
  • similar acid-base reaction
  • Redox: 2 HBr + H2SO4 –> Br2(g) + SO2 (g) + 2H2O (l)
  • Observations: white steamy HBr fumes, orange fumes of Br and colourless, acidic gas SO2
  • H2SO4 acts as an acid in the first reaction but then an oxidising agent in the redox step.
54
Q

Reactions of halide ions with conc. H2SO4- Iodide ions

A

-Strongest halide reducing agent. Reduces S from +6 in H2O4, to +4 in SO2, to 0 in S and -2 in H2S

55
Q

Reactions of iodide ions with conc. H2SO4- equations and observations

A

1) NaI(s) + H2SO4(l) –> NaHSO4(s) + HI(g)
- O: white steamy fumes of HI
2) 2 HI + H2SO4–> I2(s) + SO2(g) + 2 H2O(l)
- O: Black solid and purple fumes of iodine
3) 6 HI + H2SO4 –> 3 I2 + S (s) + 4 H2O (l)
- O: colourless, acidic SO2 gas
4) 8 HI + H2SO4 –> 4 I2(s) + H2S(g) + 4 H2O(l)
- O: H2S gas with bas egg smell

56
Q

What is disproportionation?

A

Reaction where an element is simultaneously oxidised and reduced
e.g. chlorine with water
Cl2
(g) + H2O (l) ⇌ HClO (aq) + HCl (aq)

57
Q

Reaction of chlorine with water in sunlight

A

Chlorine bubbled through water in presence of sunlight.
2Cl2 + 2H2O –> 4H+ + 4Cl
- + O2
-Green colour of chlorine water fades as CL2 reacts and colourless O2 gas produces

58
Q

What is chlorine used for?

A

Water treatment to kill bacteria. Used to treat drinking water and water in swimming pools. Health of water treatment outweighs the toxic effects.

59
Q

Reaction of chlorine with cold dil. NaOH solution

A

-Cl2 (and Br2, I2) in aqu. sol. react with it. The colour od the halogen sol. fades to colourless.
Cl2
(aq) + 2 NaOH (aq) –> NaCl (aq) + NaClO (aq) + H2O (l)
-Mixture of NaCl and NaClO is used as bleach and to disinfect/kill bacteria

60
Q

Reaction of sodium with cold water- observations and equation

A
  • Fizzes around the surface

- 2 Na (s) + 2 H2O (l) –> 2 NaOH (aq) + H2(g)

61
Q

Reaction of magnesium with cold water and steam- observations and equation

A

-Reacts slowly to form a hydroxide but with steam, it reacts more readily to form an oxide
Mg (s) + H2O (g) –> MgO (s) + H2(g)

62
Q

What do the elements in period 3 react with oxygen to produce?

A

Oxides

63
Q

Reaction of sodium with oxygen

A

Burns with yellow flame to form a white solid

4Na (s) + O2 (g) –> 2 Na2O (s)

64
Q

Reaction of Mg, Al, Si and P with oxygen

A

Burn with white flame to give white solid smoke

  • 2Mg (s) + O2 (g)–> 2MgO (s)
  • 4Al + 3O2 (g)–> 2Al2O3(s)
  • Si + O2 (g) –> SiO2 (s)
  • 4P + 5O2 (g)–> P4O10 (s)
65
Q

Reaction of sulfur with oxygen

A

Burns with blue flame to form acidic choking gas

66
Q

Which period 3 oxides are ionic? Explain why.

A

Metal oxides: magnesium, sodium and aluminium oxides
-Have high melting points and giant ionic lattice structures. Strong forces of attraction between ions. Ionic due to large diff. in electronegativity between the metal and O. Increased charge of the cation makes ionic forces stronger from Na-Al which increases melting points.

67
Q

What is different about Al203 properties?

A

It is ionic but shows covalent characteristics. This is due to electronegativity diff. being less big or the small Al ion with a high charge is able to get close to the oxide and distort the oxide charge cloud

68
Q

Which period 3 oxide is macromolecular?

A

SiO2- has many very strong covalent bonds between atoms. High energy required to break them so v. high mp and bp.

69
Q

Which period 3 oxides are simple molecular oxides?

A

P4O10, SO2: have weak IMFS (VDWs and permanent dipoles) so have lower mps. They are covalent due to small electronegativity diff. between non-metal and O atoms. As P4O10 is bigger, it has larger VDWs and higher mp.

70
Q

How is aluminium metal protected from corrosion in moist air?

A

Using a thin layer of aluminium oxide- high lattice strength of Al2O3 and its insolubility in water to make the layer impermeable to air and water.

71
Q

How do metal ionic period 3 oxides react with water?

A

They form hydroxides that are alkaline.
pH decreases across the period as reactions get less vigorous

e.g. Na2O (s) + H2O (l) –> 2Na+ (aq) + 2OH- (aq)

72
Q

Why don’t Al2O3 and SiO2 dissolve in water?

A
  • Al2O3 ionic lattice has high strength
  • SiO2 macromolecular structure
  • This is why they give a neutral pH 7
73
Q

Why is MgO better than NaOH at treating acids in rivers and stomach?

A

It is sparingly soluble and weakly alkaline so using excess would not make water excessively alkaline

74
Q

How do non-metal, simple molecular, covalent period 3 oxides react with water?

A

They form acids

e.g. P4O10 (s) + 6 H2O (l) –> 4 H3PO4

75
Q

What is the trend of period 3 oxides reactions with water?

A

Ionic metal oxides show basic behaviour and non-metal covalent oxides show acidic behaviour. Aluminium oxide can show both.

76
Q

What do basic oxides react with acids to form?

A

They form salts.
eg. Na2O (s) + 2 HCl (aq)–> 2NaCl (aq) + H2O (l)

-Acid + base –> salt and water

77
Q

How does an amphoteric oxide, aluminium oxide, react as both an acid and base?

A
  • Acid: Al2O3
    (s) + 3H2SO4
    (aq) –> Al2(SO4)3 (aq) + 3H2O (l)
  • Base: Al2O3 (s)+ 2NaOH (aq) + 3H2O (l)–> 2NaAl(OH)4 (aq)
78
Q

What does SiO2 react with, if not water?

A
  • With conc. NaOH
  • It is still classified as an acidic oxide regardless

e.g. Al2O3 (s)+ 2NaOH (aq) + 3H2O (l) –> 2NaAl(OH)4 (aq)

AQA A Level Chemistry (14 decks)

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