Edexcel International GCSE Chemistry Section 2: Inorganic Chemistry Exam Questions

About Edexcel International GCSE Chemistry Section 2: Inorganic Chemistry

Section 2 of Edexcel International GCSE Chemistry (4CH1) applies the principles from Section 1 to real elements and compounds. You study the alkali metals and halogens, the gases in the atmosphere including the oxygen content of air and carbon dioxide, the reactivity series and rusting, the extraction and uses of metals, acids, alkalis and titrations, the preparation of soluble and insoluble salts, and the chemical tests for gases, ions and water. It is assessed on both papers, with bold content on Paper 2 only. Examiners frequently ask for observations, practical methods for salt preparation and the precise results of chemical tests.

What you need to know

• Group 1 Lithium, sodium and potassium react with water to form hydroxides and hydrogen, with reactivity increasing down the group because the outer electron is further from the nucleus and more easily lost.
• Group 7 Chlorine is a pale yellow-green gas, bromine a red-brown liquid and iodine a dark grey solid. Reactivity decreases down the group; a more reactive halogen displaces a less reactive one from its halide solution, which is a redox reaction.
• Gases in the atmosphere Air is about 78% nitrogen, 21% oxygen, 0.9% argon and 0.04% carbon dioxide. The percentage of oxygen can be found by reacting air with copper, iron or phosphorus and measuring the volume decrease. Carbon dioxide is made by thermal decomposition of metal carbonates and is a greenhouse gas.
• Reactivity series and rusting Potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold, deduced from reactions with water, acids and displacement. Rusting of iron needs oxygen and water; prevention includes barrier methods, galvanising and sacrificial protection.
• Extraction and uses of metals The method of extraction depends on the metal's position in the reactivity series: metals below carbon can be extracted by reduction with carbon, while more reactive metals such as aluminium are extracted by electrolysis. Uses of aluminium, copper and iron (steel) relate to their properties.
• Acids, alkalis and titrations Acids are proton (H+) donors and bases are proton acceptors. Indicators include litmus, phenolphthalein and methyl orange; pH can be measured with universal indicator. Titrations are used to find the volumes of acid and alkali that react exactly.
• Salts and chemical tests Use solubility rules to decide how to prepare a salt: excess insoluble base or metal with acid then filter and crystallise; titration for soluble salts from alkalis; precipitation for insoluble salts. Tests include flame tests, sodium hydroxide for cations, tests for carbonate, sulfate and halide ions, gas tests, and anhydrous copper(II) sulfate (white to blue) for water.

Common mistakes in Section 2: Inorganic Chemistry

• Saying halogen reactivity increases down the group. It decreases, because it is harder to gain an electron.
• Giving 20% or 80% instead of the expected 21% oxygen and 78% nitrogen when the question asks for percentages in air.
• Adding hydrochloric acid in the halide test. Use dilute nitric acid before silver nitrate.
• Confusing iron(II) hydroxide (green) and iron(III) hydroxide (brown) precipitates.
• Saying anhydrous copper(II) sulfate tests for pure water. It shows water is present; boiling point (100 °C) shows it is pure.

Try three Section 2: Inorganic Chemistry exam-style questions