StemUp: Edexcel A A level Chemistry Topic 4: Inorganic Chemistry and the Periodic Table

Explain the trend in first ionisation energy down group 2? (4)

- First ionisation energy decreases

down the group.

- Down the group, atomic radius and shielding increase (which overpowers the effect of increasing nuclear charge).

- Therefore, the outer electrons feel a weaker electrostatic attraction to the nucleus.

- So it is easier to remove an electron.

Explain the trend in reactivity down group 2? (4)

- Reactivity increases down the group

Down the group, atomic radius and shielding increase (which overpowers the effect of increasing nuclear charge)

Therefore, the outer electrons feel a weaker electrostatic attraction to the nucleus

So the outer electrons can more easily be lost, so the metal is more reactive (group 2 metals react by losing the two electrons in their outer shells)

Give the chemical equation for the general reaction of group 2 metals with oxygen? (1)

2M (s) + O2 (g) → 2MO (s)

Give the chemical equation(s) for the reaction of strontium, Sr, with oxygen? (2)

2Sr (s) + O2 (g) → 2SrO (s)

Sr (s) + O2 (g) → SrO2 (s)

Give the chemical equation(s) for the reaction of barium, Ba, with oxygen? (2)

2Ba (s) + O2 (g) → 2BaO (s)

Ba (s) + O2 (g) → BaO2 (s)

Give the chemical equation for the general reaction of group 2 metals with water? (1)

M (s) + 2H2O (l) → M(OH)2 (s) + H2 (g)

Describe the reaction of magnesium with cold water, including the chemical equation? (2)

Mg (s) + 2H2O (l) → Mg(OH)2 (aq) + H2 (g)

Very slow

Describe the reaction of magnesium with steam, including the chemical equation? (2)

Mg (s) + H2O (g) → MgO (s) + H2 (g)

Give the chemical equation for the general reaction of group 2 metals with chlorine? (1)

Mg (s) + Cl2 (g) → MgCl2 (s)

Give the chemical equation for the general reaction of group 2 oxides with water? (1)

MO (s) + H2O (l) → M(OH)2 (aq)

Describe the reaction of magnesium oxide with water, including the chemical equation? (2)

- MgO (s) + H2O (l) → Mg(OH)2 (s).

- MgO is only slightly soluble, so a weak alkaline solution is formed.

Describe the reaction of calcium oxide with water, including the chemical equation? (2)

- CaO (s) + H2O (l) → Ca(OH)2 (s).

- Vigorous reaction which causes some of the water to boil off (due to the large amount of energy released).

What are the products of the reaction of a group 2 oxide with hydrochloric acid? (2)

- Metal chloride.

- Water.

What are the products of the reaction of a group 2 oxide with sulphuric acid? (2)

- Metal sulphate.

- Water.

What are the products of the reaction of a group 2 hydroxide with dilute hydrochloric acid? (2)

- Metal chloride.

- Water.

What are the products of the reaction of a group 2 hydroxide with sulphuric acid? (2)

- Metal sulphate.

- Water.

Describe the trend in the solubility of group 2 hydroxides in water going down the group? (1)

Solubility of hydroxides increases down the group.

Describe the trend in the solubility of group 2 sulphates in water going down the group? (1)

Solubility decreases down the group.

Explain the trend in the thermal stability of group 1 and 2 nitrates and carbonates down the group? (5)

- Thermal stability increases down the group (higher temperature required for thermal decomposition).

- The ionic radius of cations (metals) increases down the group, but the charge remains the same.

- Charge density decreases down the group so the cation becomes less electronegative

- Less polarisation (and therefore less weakening) of the N-O / C-O bond.

- More heat energy is required to break the bonds therefore more thermally stable down the group.

Give the general chemical equation for the thermal decomposition of group 2 carbonates? (1)

XCO3 (s) —> XO (s) + CO2 (g)

How can carbon dioxide, CO2, be tested for? (2)

- Limewater.

- It turns from clear to cloudy.

Give the general chemical equation for the thermal decomposition of group 1 nitrates? (1)

2XNO3 (s) —> 2XNO2 (s) + O2 (g)

How can nitrogen dioxide, NO2, be observed? (1)

Reddish-brown fumes

How can oxygen, O2, be tested for? (2)

- Glowing splint.

- Is relit.

Give the chemical equation for the thermal decomposition of lithium nitrate, Li(NO3)2? (1)

4LiNO3 (s) —> 2Li2O (s) + 4 NO2 (g) + O2 (g)

Give the general chemical equation for the thermal decomposition of group 2 nitrates? (1)

2X(NO3)2 (s) —> 2XO (s) + 4NO2 (g) + O2 (g)

Explain the difference between the thermostability of group 1 and 2 carbonates? (3)

- Group 2 metal ions have a higher charge, and therefore a higher charge density.

- In group 2 carbonates there is more polarisation and weakening of the C-O bonds.

- Less energy is required to break bonds, so group 2 carbonates are less thermally stable.

What conditions are used for thermal decomposition? (2)

- Aerobic conditions (plenty of oxygen).

- Heat.

Explain how flame tests produce a coloured flame? (4)

- Heat energy (from the flame).

- Excites electrons to a higher energy level.

- As they cool, electrons drop back down to ground state.

- As they drop down to ground state, they emit energy in the form of visible light.

Why do different ions produce differently coloured flames? (2)

- Electrons are dropping between different energy levels.

- So they emit different wavelengths of light, which produce different colours.

Describe how a flame test is carried out? (3)

- Nichrome/platinum wire.

- Dipped in concentrated hydrochloric acid.

- The wire is then dipped in the solid and held over a non-luminous bunsen flame.

Why does the wire used in a flame test have to be nichrome or platinum? (3)

- Unreactive.

- High melting point.

- Doesn't have its own flame colour.

Why is the wire dipped in hydrochloric acid before carrying out a flame test? (1)

To clean the wire/remove contaminants.

What is the flame colour for lithium, Li+? (1)

Red

What is the flame colour for sodium, Na+? (1)

Yellow

What is the flame colour for potassium, K+? (1)

Lilac

What is the flame colour for rubidium, Rb+? (1)

Red

What is the flame colour for caesium, Cs+? (1)

Blue-violet

What is the flame colour for magnesium, Mg2+? (1)

Colourless

What is the flame colour for calcium, Ca2+? (1)

Brick red

What is the flame colour for strontium, Sr2+? (1)

Crimson red

What is the flame colour for barium, Ba2+? (1)

(Apple) green

What is the flame colour for copper, Cu2+? (1)

Blue-green

Explain the trend in melting/boiling points down group 7? (3)

- Melting/boiling point increases down the group.

- The number of electrons (in each atom/molecule) increases down the group.

- The strength of London forces increases down the group so more energy is required to separate the molecules.

Explain the trend in the physical state at room temperature down group 7? (2)

- Fluorine and chlorine are gases, bromine is a liquid, and iodine and astatine are solids.

- Physical state changes in this way due to increasing melting/boiling point (decreasing volatility) down the group.

Describe the appearance of fluorine at room temperature? (1)

Pale yellow gas.

Describe the appearance of chlorine at room temperature? (1)

Greenish-yellow gas.

Describe the appearance of bromine at room temperature? (1)

Orange-brown liquid.

Describe the appearance of iodine at room temperature? (1)

Grey solid (easily warmed to give off purple vapours).

Explain the trend in electronegativity down group 7? (3)

- Atomic radius and shielding increase down the group (which overpowers the effect of increasing nuclear charge).

- Electrons feel a weaker electrostatic attraction to the nucleus.

- Therefore electronegativity decreases down the group.

Explain the trend in reactivity down group 7? (3)

- Reactivity decreases down the group.

- Atomic radius and shielding increase down the group.

- Therefore it is harder to attract an electron (group 7 elements react by gaining an electron).

Explain the trend in the oxidising power of halogens down group 7? (3)

- Halogens act as oxidising agents as they accept electrons.

- Down the group atomic radius and shielding increase so it is harder to attract electrons.

- Therefore oxidising power decreases down the group.

Explain the trend in the reducing power of halide ions down group 7? (3)

- Halides act as reducing agents as they donate electrons.

- Down the group atomic radius and shielding increase so it is easier to lose electrons.

- Therefore reducing power increases down the group.

Explain which halogens will displace which halides? (2)

- A halogen higher in the group will displace a halide lower in the group.

- Because it has a higher oxidising strength (it is more able to attract electrons).

What type of reaction is a halogen displacement reaction? (1)

A redox reaction.

What is the colour of chlorine in aqueous solution? (1)

Pale green.

What is the colour of chlorine dissolved in an organic solvent? (1)

Pale green.

What is the colour of bromine in aqueous solution? (1)

Yellow-orange.

What is the colour of bromine dissolved in an organic solvent? (1)

Orange.

What is the colour of iodine in aqueous solution? (1)

Brown.

What is the colour of iodine dissolved in an organic solvent? (1)

Purple.

Give the chemical equation and observations of the reaction between potassium bromide, KBr, and chlorine, Cl2, in aqueous solution? (2)

2KBr (aq) + Cl2 (aq) → 2KCl (aq) + Br2 (aq)

The solution turns from pale green to yellow-orange.

What happens to the potassium chloride and bromine solution when cyclohexane is added? (1)

Turns orange (from yellow-orange).

Give the chemical equation and observations of the reaction between potassium iodide, KI, and chlorine, Cl2, in aqueous solution? (2)

2KI (aq) + Cl2 (aq) → 2KCl (aq) + I2 (aq)

The solution turns from pale green to brown.

What happens to the potassium chloride and iodine solution when cyclohexane is added? (1)

Turns purple (from brown).

Give the chemical equation and observations of the reaction between potassium iodide, KI, and bromine, Br2, in aqueous solution? (2)

2KI (aq) + Br2 (aq) → 2KBr (aq) + I2 (aq)

The solution turns from yellow-orange to brown.

What happens to the potassium bromide and iodine solution when cyclohexane is added? (1)

Turns purple (from brown).

What type of compound is formed by the reaction of a halogen with a group 1 or 2 metal ? (1)

Metal halide salts.

Give the chemical equation for the reaction of sodium with chlorine? (1)

2Na (s) + Cl2 (g) → 2NaCl (s)

Give the chemical equation for the reaction of calcium with bromine? (1)

Ca (s) + Br2 (l) → CaBr2 (s)

What type of reaction occurs between group 1 and 2 metals and a halogen? (1)

A redox reaction.

What is the role of the halogen when it is reacted with a group 1 or 2 metal? (2)

- It acts as an oxidising agent.

- It accepts electrons from the metal.

What is the change in the oxidation number of group 1 and 2 metals when reacted with a halogen? (1)

Oxidation number increases (loses electrons).

What is the change in the oxidation number of halogens when reacted with a group 1 or 2 metal? (1)

Oxidation number decreases (gains electrons).

Give the chemical equation for the disproportionation reaction of chlorine, Cl2, with water, H2O? (1)

Cl2 (aq) + H2O (l) → HCl (aq) + HClO (aq)

Explain, using oxidation numbers, why the reaction between chlorine and water is a disproportionation reaction? (3)

- The oxidation number of Cl increases from 0 in Cl2 to +1 in HClO, so it is being oxidised.

- The oxidation number of Cl decreases from 0 in Cl2 to -1 in HCl, so it is being reduced.

- Therefore the same species (Cl) is being oxidised and reduced at the same time.

Explain, including a chemical equation, the use(s) of HClO? (2)

HClO (aq) → H+ (aq) + ClO- (aq)

HClO and ClO- sterilise water by killing bacteria

Give the chemical equation for the disproportionation reaction of chlorine, Cl2, with cold, dilute sodium hydroxide, NaOH? (1)

Cl2 (aq) + 2NaOH (aq) → NaCl (aq) + NaClO (aq) + H2O (l)

Explain, using oxidation numbers, why the reaction between chlorine and cold, dilute sodium hydroxide is a disproportionation reaction? (3)

- The oxidation number of Cl increases from 0 in Cl2 to +1 in NaClO, so it is being oxidised.

- The oxidation number of Cl decreases from 0 in Cl2 to -1 in NaCl, so it is being reduced.

- Therefore the same species (Cl) is being oxidised and reduced at the same time.

Describe the use(s) of NaClO? (1)

Used in bleach.

Give the chemical equation for the disproportionation reaction of chlorine, Cl2, with hot, concentrated sodium hydroxide, NaOH? (1)

3Cl2 (aq) + 6NaOH (aq) → 5NaCl (aq) + NaClO3 (aq) + 3H2O (l)

Explain, using oxidation numbers, why the reaction between chlorine and hot, concentrated sodium hydroxide is a disproportionation reaction? (3)

- The oxidation number of Cl increases from 0 in Cl2 to +5 in NaClO3, so it is being oxidised.

- The oxidation number of Cl decreases from 0 in Cl2 to -1 in NaCl, so it is being reduced.

- Therefore the same species (Cl) is being oxidised and reduced at the same time.

Describe the use(s) of NaClO3? (1)

Used in herbicides/weed killers.

Give the chemical equation for the reaction between sodium chloride, NaCl, and concentrated sulphuric acid, H2SO4? (1)

NaCl (s) + H2SO4 (aq) → NaHSO4 (aq) + HCl (g)

What type of reaction occurs between sodium chloride, NaCl, and concentrated sulphuric acid, H2SO4? (1)

Acid-base reaction.

Why does a redox reaction not occur between sodium chloride, NaCl and concentrated sulphuric acid, H2SO4? (1)

Chloride ions (Cl-) are not a strong enough reducing agent to reduce sulphuric acid.

What are the observations (and relevant compounds) of the reaction between sodium chloride, NaCl, and concentrated sulphuric acid, H2SO4? (1)

Misty fumes (HCl).

Give the chemical equations for the reactions between sodium bromide, NaBr, and concentrated sulphuric acid, H2SO4? (2)

NaBr (s) + H2SO4 (aq) → NaHSO4 (aq) + HBr (g)

2HBr (aq) + H2SO4 (aq) → Br2 (g) + SO2 (g) + 2H2O (l)

What type of reaction occurs between sodium bromide, NaBr, and concentrated sulphuric acid, H2SO4? (1)

Acid-base reaction.

What type of reaction occurs between hydrogen bromide, HBr, and concentrated sulphuric acid, H2SO4? (1)

Redox reaction.

Describe the changes in oxidation numbers in the reaction between hydrogen bromide, HBr, and concentrated sulphuric acid, H2SO4? (2)

- The oxidation number of Br increases from -1 in HBr to 0 in Br2 (oxidation).

- The oxidation number of S decreases from +6 in H2SO4 to +4 in SO2 (reduction).

What are the observations (and relevant compounds) of the reactions between sodium bromide, NaBr, and concentrated sulphuric acid, H2SO4? (3)

- Misty fumes (HBr).

- Reddish-brown gas (Br2).

- Colourless gas with a choking smell (SO2).

Why can HBr react with concentrated sulphuric acid when HCl cannot? (1)

Br- is a stronger reducing agent than Cl-.

Give the chemical equations for the reactions between sodium iodide, NaI, and concentrated sulphuric acid, H2SO4? (4)

NaI (s) + H2SO4 (aq) → NaHSO4 (aq) + HI (g)

2HI (aq) + H2SO4 (aq) → I2 (g) + SO2 (g) + 2H2O (l)

6HI (aq) + H2SO4 (aq) → 3I2 (g) + S (s) + 4H2O (l)

8HI (aq) + H2SO4 (aq) → 4I2 (g) + H2S (s) + 4H2O (l)

What type of reaction occurs between sodium iodide, NaI, and concentrated sulphuric acid, H2SO4? (1)

Acid-base reaction.

What type of reaction occurs between hydrogen iodide, HI, and concentrated sulphuric acid, H2SO4? (1)

Redox reaction.

Describe the changes in oxidation numbers in the reactions between hydrogen iodide, HI, and concentrated sulphuric acid, H2SO4? (4)

- The oxidation number of I increases from -1 in HI to 0 in I2 (oxidation).

- The oxidation number of S decreases from +6 in H2SO4 to +4 in SO2 (reduction).

- The oxidation number of S decreases from +6 in H2SO4 to 0 in S (reduction).

- The oxidation number of S decreases from +6 in H2SO4 to -2 in H2S (reduction).

What are the observations (and relevant compounds) of the reactions between sodium iodide, NaI, and concentrated sulphuric acid, H2SO4? (4)

- Misty fumes (HI).

- Purple vapours (I2).

- Colourless gas with a choking smell (SO2).

- Colourless gas with rotten egg smell (H2S).

Why does HI produce S and H2S as well as SO2, whilst HBr only produces SO2? (1)

I- is a stronger reducing agent than Br-

Describe how silver nitrate can be used to produce precipitates of halide ions? (3)

- Nitric acid, HNO3, is added to the halide.

- Silver nitrate, AgNO3, is added to the solution.

- Which produces a silver halide precipitate, AgX.