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Chemistry A - Level > Topic 4 (Group 1 and 2) - Inorganic Chemistry and the Periodic Table > Flashcards

Topic 4 (Group 1 and 2) - Inorganic Chemistry and the Periodic Table Flashcards

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1
Q

What are the group 2 elements also known as?

A

The Alkali Earth Metals

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2
Q

What charge of ions do metals in group 2 form?

A

2+

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3
Q

Describe an explain the first and second ionisation energies down the group 2 elements

A
  • The first and second ionisation energies decrease
  • Increase in distance between nucleus and valence electrons
  • Shielding increases as the number of filled shells increases, therefore the effective nuclear charge decreases
  • The effect of the increased shielding outweighs the increase in nuclear charge of the element
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4
Q

Describe an explain the trend in ionic radii down the group 2 elements

A
  • Ionic radius increases
  • The number of filled inner shells increases
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5
Q

Describe an explain the trend in reactivity down the group 2 elements

A
  • Reactivity increases
  • Due to it becoming easier for the valence electrons to be lost as the EFA’s between these electrons and the nucleus decreases
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6
Q

What oxidation states do metals in group 2 form? Why?

A

+2, as 2 electrons are lost from the outer s orbital

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7
Q

Compare the size of the group 2 ions to their atoms

A
  • Group 2 ions are smaller than their atoms
  • No. of electrons has decreased but the nuclear charge is still the same for each ion
  • The valence electrons are closer to the nucleus
  • Less shielding from filled inner shells
  • Therefore, EFA’s between the nucleus and valence electrons has increased
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8
Q

Compare the ionic radii of the group 1 metals versus the group 2 metals?

A

As you go down the group the radii of the groups 1 ions will increase more than the radii of the group 2 metals. This is because group 2 ions have a greater nuclear charge so there are stronger EFA’s between the outer electrons and the nucleus.

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9
Q

Do the group 2 metals react with water/steam?

A

yes

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10
Q

Are the reactions of group 2 metals with water/steam more or less vigorous than with group 1 metals?

A

less vigorous

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11
Q

Which group 2 elements react with water/steam?

A

Mg -> Ba

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12
Q

Does Be react with water/steam?

A

no - it requires temperatures of 750 degrees C to react as the sum of the 1st and 2nd ionisation energies is much larger comparative to the other group 2 elements

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13
Q

What do group 2 metals act as in reactions?

A

reducing agents (they are oxidised)

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14
Q

What are the observations of the group 2 elements Be -> Ba when reacted with cold water

A

Be - unreactive
Mg - almost unreactive (some bubbles of hydrogen form on the surface, sight dip in water level)
Ca - hydrogen bubbles (effervescence) produced, white ppt. of Ca(OH)2 formed
St - many hydrogen bubbles ( vigorous effervescence) produced, white ppt. of St(OH)2 formed
Ba - most hydrogen bubbles (most vigorous effervescence) produced, white ppt. of Ba(OH)2 formed

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15
Q

How much white solid do you observe from the reaction of group 2 metals with cold water as you go down the group?

A

Less as you go down the group - the white solid becomes more soluble in the alkali solution

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16
Q

Write the equation for the reaction of Magnesium with cold water?

A

Mg(s) + 2H2O (l) -> Mg(OH)2 (s) + H2 (g)

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17
Q

What type of solution is formed form the reaction of group 2 elements with cold water?

A

Alkaline solutions

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18
Q

Write the general equation for the reaction of Ca, St and Ba with cold water?

A

M (s) + 2H2O (l) -> M(OH)2 (aq or s) + H2 (g)

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19
Q

What is the main difference between the reactions of group 2 metals with cold water versus with steam? Why?

A

The reactions are a lot more vigorous with steam as a greater proportion of particles have the required Ea to react

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20
Q

What are the observations of the group 2 elements Be -> Ba when reacted with steam?

A

Be - unreactive
Mg - bright white flame, white powder of MgO, hydrogen gas produced
Ca - white powder of CaO, hydrogen gas produced
St - white powder of StO, hydrogen gas produced
Ba - white powder of BaO, hydrogen gas produced

NB: Reactivity still increases down the group

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21
Q

Describe the set up for the reaction of Group 2 metals with steam

A
  • Horizontal test tube with wool soaked in water at the curved end of it
  • The test tube is fitted with a bung with tubing connected to a downturned test tube in water
  • The group 2 metal is placed in the centre of the horizontal test tube
  • The water soaked wool is then heated using a bunsen burner
  • Effervescence should be produced in the downturned test tube
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22
Q

Write the general equation for the reaction of Ca, St and Ba with steam

A

M (s) + H2O (g) -> MO (s) + H2 (g)

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23
Q

Which group 2 metals burn in oxygen?

A

Mg -> Ba

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24
Q

Write the general equation for the reaction of group 2 metals with oxygen

A

2M (s)+ O2 (g) -> 2MO (s)

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25
Q

What are the observations for each of the reactions of group 2 metals with oxygen?

A

Mg - Bright white flame, white solid produced
Ca - Bright red flame, white solid produced
St - Bright white flame (red tinges around the edges), white solid produced
Ba - Bright green flame

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26
Q

Which group 2 metals from a different compound when burnt in an excess of oxygen?

A

St and Ba

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27
Q

Write a general equation for the reaction of group 2 metals with excess oxygen

A

M (s) + O2 (g) -> MO2 (s)

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28
Q

What is the peroxide ion?

A

O2 (2-)

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29
Q

What is the definition of a basic oxide?

A

A metal oxide that reacts with acids to form salts and water.

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30
Q

What is the definition of an alkali?

A

A soluble base

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31
Q

What is the definition of a base?

A

A proton accepter

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32
Q

Which group 2 metals react with Cl2?

A

All of them

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33
Q

Write a general equation for the reaction of the group 2 elements with chlorine

A

M (s) + Cl2(g) -> MCl2 (s)

34
Q

What conditions do you need to provide in order for the group 2 elements to react with chlorine?

A

Heat

35
Q

What is the observation when group 2 elements reaction with chlorine upon heating?

A

A white solid forms

36
Q

Which metal oxides in group 2 act as basic oxides?

A

Mg -> Ba

37
Q

What group 2 compounds act as bases in neutralisation reactions with dilute acids?

A

oxides and hydroxides

38
Q

Write the general reaction of group 2 oxides with water

A

MO (s) + H2O (l) -> M(OH)2 (aq)

39
Q

Write the equation for the reaction Barium Hydroxide with Hydrochloric Acid

A

Ba(OH)2 (s) + 2HCl (aq) -> BaCl2 (aq) + 2H2O (l)

40
Q

Write the equation for the reaction of Magnesium Oxide with Hydrochloric Acid

A

MgO (s) + 2HCl (aq) -> MgCl2 (aq) + H2O (l)

41
Q

What is the general equation for a neutralisation reaction?

A

acid + base -> salt + water

42
Q

What is the general equation for a metal + acid reaction?

A

metal + acid -> salt + hydrogen

43
Q

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

A

solubility increases

44
Q

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

A

solubility decreases

45
Q

What is the way to remember the solubility rules?

A

HAM SALAD
hydroxides are more, sulphates are less, as descended

46
Q

What is the use of the insoluble compound barium sulphate?

A

As a medical tracer for x-ray imaging as it cant be absorbed into the blood

47
Q

What is the test for sulphate ions?

A
  • Add a few drops of HCl to your solution containing sulphate ions
  • Add a soluble barium salt e.g barium chloride or barium nitrate
  • A white ppt. of barium sulphate forms if sulphate ions are present
48
Q

Why do you need to add a few drops of HCl to your solution containing sulphate ions before adding your soluble barium salt?

A

To remove any carbonate impurities as these would produce a false positive (a white ppt.) when the barium compound was added

49
Q

What is the general equation for an acid + carbonate reaction?

A

acid + carbonate -> salt + carbon dioxide + water

50
Q

What is the ionic equation for barium and sulphate ions in the test for sulphate ions?

A

Ba(2+) (aq) + SO4(2-) (aq) -> BaSO4 (s)

51
Q

How do you test for the trends in solubility of the group 2 hydroxides and sulphates?

A
  • Add solutions of your group 2 metal chlorides to test tubes
  • Add drops of hydroxide and sulphate solutions to each of them individually and record how many drops it takes for a ppt. to appear
52
Q

Describe how to conduct a flame test

A
  • Take a nichrome (or platinum) wire and dip it in conc. HCl. Hold the wire above the cone of the roaring bunsen burner. Repeat until the wire is clean/ no colour is observed when doing this.
  • Dip the wire into the conc. HCl and then into a small amount of the compound that you are analysing. Hold the sample in the flame and note the colour that the flame turns
  • Clean the wire thoroughly so that no traces of that compound remain (step 1)
  • repeat the experiment with other compounds
53
Q

What are the colours produced in the flame test for:
sodium
lithium
potassium
magnesium
calcium
strontium
barium
copper

A

sodium - strong persistent yellow
lithium - scarlet red
potassium - lilac
magnesium - no colour
calcium - brick red
strontium - red
barium - green
copper - blue/green

54
Q

Why, when conducting a flame test, do you have to dip the nichrome wire in conc. HCl twice?

A

1 - To remove impurities from other compounds
2 - to form a volatile chloride with the compound you are testing -> this gives a clearer colour

55
Q

Why do we observe different colours for different compounds during a flame test?

A
  • When the electrons are heated they get excited and absorb energy. This causes them to go form a ground state to a higher energy orbital.
  • When the electrons de-excite they release this energy
  • The energy released corresponds to a specific wavelength of light from the visible light spectrum -> hence we observe that colour
56
Q

Why does magnesium not produce a colour in the flame test?

A

As the wavelength emitted when the electron de-excites is outside of the visible spectrum

57
Q

What is the definition of thermal stability?

A

An indication of the ease by which compounds decompose upon heating

58
Q

Which compounds of group 1 and 2 metals undergo thermal decomposition?

A

Nitrates and Carbonates

59
Q

What is the definition of thermal decomposition?

A

The breaking down of 1 compound into 2 or more products by heat

60
Q

What is the general equation for the thermal decomposition of group 2 carbonates?

A

MCO3 -> MO + CO2

metal carbonate -> metal oxide + carbon dioxide

61
Q

What is the general equation for the thermal decomposition of group 2 nitrates?

A

2M(NO3)2 -> 2MO + 4NO2 + O2

metal nitrate -> metal oxide + nitrogen dioxide + oxygen

62
Q

What is the general equation for the thermal decomposition of group 1 nitrates?

A

2MNO3 -> 2MNO2 + O2

metal nitrate -> metl nitrite + oxygen

63
Q

Why wont group 1 carbonates undergo thermal decomposition upon heating in a lab?

A

They require extremely high temperatures to do so

64
Q

Which element in group 1 follows the same decomposition reactions as group 2?

A

lithium

65
Q

Write the equation for the thermal decomposition of lithium nitrate

A

4LiNO3 -> 2Li2O + 4NO2 + O2

66
Q

What is the trend in thermal stability as you go down groups 1 and 2?

A

The compounds become more thermally stable - require more heat energy to undergo thermal decomposition

67
Q

What two factors affect thermal stability of compounds?

A

The:
- Charge of the cation
- Ionic radius of the cation

68
Q

What is the term used to describe how easily a cation can distort an anion?

A

polarising power

69
Q

What is the definition of polarising power?

A

The indication of the extent to which cations are able to distort the negative electron cloud around a neighbouring anion

70
Q

Explain why thermal stability decreases as you ascend groups 1 and 2

A
  • As you ascend the group the ionic radius increases
  • The ions are more charge dense, therefore, their polarising power increases and the anion is distorted more
  • The X - O bonds in the anion are weakened more, meaning that less heat energy is required to break down the compound
71
Q

Why are group 1 nitrates more thermally stable than group 2 nitrates?

A

As there ions only have a 1+ charge, therefore the NO3(-) ions are less polarised so the N - O bonds are weakened less

72
Q

Which group of nitrates/carbonates will, in general, require more heat energy to undergo thermal decomposition?

A

Group 1

73
Q

What is an ionic equation?

A

An equation that describes a full chemical equation by only showing the reacting ions in solution. These equations should be balanced for both reacting moles and charges.

74
Q

What is the definition of a spectator ion?

A

An ion which are present in the solution but do not take part in the reaction (ions that do not have a change of state or oxidation state)

75
Q

What is the definition of an ionic precipitation reaction?

A

A reaction which produces a solid ppt. on mixing 2 solutions containing ions

76
Q

What are the solubility rules?

A

NITRATES - All soluble
CHLORIDES - All soluble EXCEPT lead and silver
SULPHATES - All soluble EXCEPT lead, calcium and barium
POTASSIUM, AMMONIUM AND SODIUM SALTS - All soluble

CARBONATES - All insoluble EXCEPT PAS salts
HYDROXIDES/ OXIDES - All insoluble EXCEPT PAS salts

NB: calcium hydroxide is slightly soluble

77
Q

Describe the set up and the variables for the practical: Investigating the Thermal Decomposition of Carbonates

A

INDEPENDANT VARIABLE: metal carbonate
DEPENDANT VARIABLE: time taken for the limewater to turn cloudy
CONTROL VARIABLES:
- distance between flame and test tube
- same moles of metal carbonate
- same volume and conc. of limewater

SET UP:
- Attach a test tube with you metal carbonate inside horizontally to a clamp with a bung
- Have a delivery tube going from the bung to a test tube filled with limewater
- Heat the metal carbonate using a bunsen burner and time how long it takes for the limewater to turn cloudy
- Repeat for all the metal carbonates in the group

78
Q

What is the independent variable?

A

The variable that you change

79
Q

What is the dependent variable?

A

The variable that you measure

80
Q

What are the observations in the practical: Investigating the Thermal Decomposition of Carbonates

A

GROUP 2 CARBONATES (NOT THERMALLY STABLE)
- Bubbles are produced
- Limewater turns cloudy
- powder moves up beaker

GROUP 1 CARBONATES (THERMALLY STABLE
- does not react

81
Q

What are the two ways that you can determine the time taken for the metal nitrate to decompose in the practical: Investigating the Thermal Decomposition of Nitrates

A

Test for Oxygen: Put a glowing splint into the test tube containing the unknown gas, if O2 is present then the splint will relight

Test for Nitrogen dioxide:
- Brown gas so can visually see
- NO2 is slightly acidic so should turn damp blue litmus paper red

Chemistry A - Level (26 decks)

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