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A Level Chemistry > Elements of Group 1 and 2 - Inorganic chemistry > Flashcards

Elements of Group 1 and 2 - Inorganic chemistry Flashcards

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1
Q

What is the bonding in the group 1 and 2 elements?

A

Metallic

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2
Q

What are the reasons for the trend in melting and boiling point and hardness of group 1 and 2 metals?

A

Metallic radius increases down the group due to the extra electron shells, so the metallic bonding weakens down the group, and so melting, boiling points and hardness all decrease down the group

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3
Q

Why are group 2 metals harder than group 1 metals and have higher melting and boiling points?

A

Number of valency electrons increases and metallic radius slightly decreases, so the strength of the metallic bonding increases

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4
Q

What are the reasons for the trend in ionisation energies down group 1 and 2?

A

The increase in nuclear charge is outweighed by the increased distance between the electron being lost and the nucleus, and the increased shielding effect of complete shells of electrons between the electron being lost and the nucleus

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5
Q

What is lithium’s flame test colour?

A

(Carmine) red

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6
Q

What is sodium’s flame test colour?

A

Intense yellow

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7
Q

What is potassium’s flame test colour?

A

Lilac

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8
Q

What is magnesium’s flame test colour?

A

No colour

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9
Q

Why does magnesium’s flame test not produce a colour?

A

The energy emitted has a wavelength outside the visible spectrum

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10
Q

What is calcium’s flame test colour?

A

Brick red

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11
Q

What is strontium’s flame test colour?

A

Red/Crimson

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12
Q

What is barium’s flame test colour?

A

(Apple) green

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13
Q

What is rubidium’s flame test colour?

A

Red

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14
Q

What is caesium’s flame test colour?

A

(Sky) blue

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15
Q

What is beryllium’s flame test colour?

A

No colour

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16
Q

Why do flame tests work?

A

Electrons are excited to a higher energy level by the Bunsen burner flame, and as they fall back down to their ground state (they are unstable in the higher energy state), they emit energy in the form of visible light

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17
Q

How should a flame test be carried out?

A

1) Use a nichrome wire (very unreactive and so cannot give out a flame colour)
2) Dip the wire in concentrated hydrochloric acid (out it in the flame to check if any colour is being produced, keep cleaning it until there isn’t one)
3) Grind up any solid that isn’t already a powder
4) Dip the wire in the solid’
5) Put the wire into the flame so a colour is produced

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18
Q

What colour does magnesium burn in oxygen?

A

Intense white light

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19
Q

What colour does calcium burn in oxygen?

A

Brick red flame

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20
Q

What colour does strontium burn in oxygen?

A

Dark red flame

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21
Q

What colour does barium burn in oxygen?

A

Pale green flame

22
Q

What compound do all group 2 metals form when they react with chlorine?

A

MCl2

Beryllium forms a covalent, anhydrous chloride, all others produce ionic chlorides

23
Q

Beryllium’s reaction with water

A

There is no reaction

24
Q

Magnesium’s reaction with water

A

Magnesium reacts very slowly with cold water, but burns when heated in steam
Mg (s) + H2O (g) -> MgO (s) + H2 (g)

25
Q

Calcium, strontium and barium’s reactions with water

A

React rapidly with cold water

Ba (s) + 2H2O (g) -> Ba(OH)2 (aq) + H2 (g)

26
Q

How does the reactivity of group 2 elements change down the group?

A

It increases

27
Q

Barium reacting with oxygen

A

2Ba (s) + O2 (g) -> 2BaO (s)

28
Q

Beryllium oxide with water

A

No reaction

29
Q

Magnesium oxide with water

A

MgO (s) + H2O (l) -> Mg(OH)2 (s)

Reacts slowly and incompletely to form a slightly alkaline suspension of magnesium hydroxide

30
Q

Calcium oxide with water

A

CaO (s) + H2O (l) -> Ca(OH)2 (s)

Reacts very exothermically to form an alkaline suspension of calcium hydroxide (limewater)

31
Q

Strontium and barium with water

A

Sr^2+ + 2OH- -> Sr(OH)2 (aq) (same for barium)

32
Q

Magnesium oxide and sulfuric acid (all group 2 metal oxides + acids)

A

MgO (s) + H2SO4 (aq) -> MgSO4 (aq) + H2O (l)
(Base + acid -> salt + water)
MgO (s) + 2H+ (aq) -> Mg^2+ (aq) + H2O (l) (sulfate ions do not change so are not included in the ionic equation)

33
Q

Calcium hydroxide and nitric acid

A

Ca(OH)2 (aq) + 2HNO3 (aq) -> Ca(NO3)2 (aq) + 2H2O (l)

2OH- (aq) + 2H+ (aq) -> 2H2O (l)

34
Q

Beryllium oxide and hydrochloric acid

A

BeO (s) + 2HCl (aq) -> BeCl2 (aq) + H2O (l)

BeO (s) + 2H+ -> Be^2+ (aq) + H2O (l)

35
Q

Why does beryllium oxide react differently?

A

It is an amphoteric oxide and so it reacts as both a base and an acid

36
Q

Reactions of group 1 oxides and hydroxides

A

All group 1 oxides react with water to give hydroxides. Group 1 hydroxides all react with acids to form salts which are soluble in water, producing alkaline solutions with a high pH

37
Q

What is the trend in solubility of the group 2 sulphates?

A

As you go down the group, the solubility of the group 2 sulfates decreases

38
Q

What is the trend in solubility of group 2 hydroxides?

A

As you go down the group, the solubility of the group 2 hydroxides increases

39
Q

What determines solubility?

A

Energy is required to break up the ionic lattice (the reverse lattice energy) and energy is given out as water molecules are attracted to the ions (hydration energy), and the solubility depends on the balance between the endothermic reverse lattice energy and the exothermic hydration energy

40
Q

Testing for sulfate ions

A

Add barium chloride or barium nitrate solution to the solution being tested, and a white ppt will form
Barium carbonate is also insoluble, so dilute hydrochloric acid is added to convert any barium carbonate to barium chloride
Ba^2+ (aq) + SO4^2- -> BaSO4 (s)

41
Q

How to distinguish between magnesium ions and barium ions

A

Adding sulfate ions: magnesium sulfate is soluble, but barium sulfate is not, so a white precipitate forms with barium sulfate, but not with magnesium sulfate
Adding hydroxide ions: Opposite to sulfate - Mg(OH)2 is insoluble and would form a white ppt

42
Q

What is the trend of thermal stability in group 1 and 2 carbonates?

A

Increases down the group, become more thermally stable and require more heat to decompose

43
Q

Thermal decomposition of group 1 carbonate

A

Li2CO3 (s) -> Li2O (s) + CO2 (g)

Only lithium carbonate decomposes in group 1, to produce lithium oxide and carbon dioxide

44
Q

Thermal decomposition of group 2 carbonates

A

MgCO3 (s) -> MgO (s) + CO2 (g)
All group 2 carbonates decompose on heating
- beryllium carbonate is so unstable it does not exist at room temperature
- barium carbonate requires extremely strong heating before it is decomposed
Group 2 carbonates decompose to from metal oxide and carbon dioxide

45
Q

What is the trend of thermal stability in group 1 and 2 nitrates?

A

Down the group, they become more thermally stable

46
Q

Thermal decomposition of lithium nitrate

A

4LiNO3 -> 2Li2O + 4NO2 + O2 (more like a group 2 nitrate)

Nitrogen dioxide is visible as a brown gas. Its decomposition is different to all other group 2 nitrates

47
Q

Thermal decomposition of other group 1 nitrates

A

2NaNO3 -> 2NaNO2 + O2

Very strong heating causes them to melt, giving off oxyden and leaving a molten nitrite

48
Q

Thermal decomposition of group 2 nitrates

A

2Ca(NO3)2 -> 2CaO + 4NO2 + O2

They all decompose to form the metal oxide, nitrogen dioxide (visible as a brown gas) and oxygen

49
Q

Explanation for the trend in thermal stability

A

From group 1 to group 2, charge density increases, and down the group charge density decreases as the ions get bigger. Ions with lower charge density polarise the anions less

50
Q

Method for investigating the thermal decomposition of carbonates

A

Heat a known mass of carbonate in a sidearm boiling tube and pass the gas produced through limewater. Time how long it takes for the first permanent cloudiness to appear. Repeat for different carbonates using the same moles of carbonate, same volume of limewater, same bunsen flame and height of the tube above the flame

51
Q

Method for investigating the thermal decomposition of nitrates

A

Set up test tube with the nitrate being tested in a clamp stand, with a bung. Start a timer when heating begins. Test for oxygen at regular intervals and look for the first signs of a brown gas, and record the time it takes for it to appear

A Level Chemistry (25 decks)

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