Key Concepts: Alkali metals and halogens show trends in reactivity. Air contains a mixture of gases. Metals can be arranged in a reactivity series based on reactions with water, acids and displacement.
Section A: Group 1 (Alkali Metals)
1. Describe the trend in reactivity down Group 1 and explain it. [3]
2. Write equations for reactions with water: lithium, sodium, potassium. [3]
Section B: Group 7 (Halogens)
3. Complete the table of halogens (colour and state at room temperature). [3]
| Halogen |
State |
Colour |
| Chlorine |
|
|
| Bromine |
|
|
| Iodine |
|
|
4. Explain why chlorine displaces bromine from potassium bromide and predict what iodine would do. [3]
Section C: Gases in the Atmosphere
5. State the approximate percentages by volume of nitrogen, oxygen, argon and carbon dioxide in dry air. [4]
6. Describe how to determine the percentage of oxygen in air using a combustion experiment. [3]
7. Write balanced equations for combustion of magnesium, hydrogen and sulfur in oxygen. [3]
8. Describe the thermal decomposition of a metal carbonate and explain why CO₂ is a greenhouse gas. [3]
Section D: Reactivity Series and Redox
9. Use the reactivity series to predict if magnesium will react with dilute hydrochloric acid and if copper will. [2]
10. Describe the conditions needed for rusting and one method of prevention. [3]
11. Define oxidation, reduction and redox in terms of oxygen and electrons. [4]
Total marks: 34
Mark Scheme
1. Reactivity increases down Group 1 because outer electron is further from nucleus and more easily lost [3]
2. 2Li + 2H₂O → 2LiOH + H₂; 2Na + 2H₂O → 2NaOH + H₂; 2K + 2H₂O → 2KOH + H₂ [3]
3. Cl₂: gas, green-yellow; Br₂: liquid, red-brown; I₂: solid, grey/purple [3]
4. Chlorine is more reactive so displaces bromine; iodine is less reactive so no displacement [3]
5. N₂ ~78%, O₂ ~21%, Ar ~0.9%, CO₂ ~0.04% (accept 0.03–0.04) [4]
6. Use copper/iron and oxygen removal in sealed apparatus; measure volume decrease; percentage oxygen = drop/total × 100 [3]
7. 2Mg + O₂ → 2MgO; 2H₂ + O₂ → 2H₂O; S + O₂ → SO₂ [3]
8. Metal carbonate → metal oxide + CO₂; CO₂ absorbs IR and contributes to greenhouse effect [3]
9. Mg reacts; Cu does not [2]
10. Rusting requires water and oxygen; prevent by painting/grease/galvanising/sacrificial protection [3]
11. Oxidation = gain of oxygen or loss of electrons; reduction = loss of oxygen or gain of electrons; redox is both occurring [4]