Pearson Edexcel International GCSE Chemistry 4CH1: Groups 1 and 7, gases, acids, salts and chemical tests – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover Topic 2 sub-topics (a) Group 1, (b) Group 7, (c) Gases in the atmosphere, (f) and (g) Acids, alkalis, bases and salts, and (h) Chemical tests (points 2.1–2.14 and 2.28–2.50) of the Pearson Edexcel International GCSE Chemistry (4CH1) specification, Issue 3 (September 2024). The qualification is untiered. Points 2.4C, 2.8C, 2.33C, 2.40C, 2.41C and 2.43C carry a C reference and are Paper 2 only; questions 2, 7 and 10 are labelled.

This set adds to the Reactivity and group trends practice set. Learn the content in the Reactivity and group trends study guide and revision notes. Course hub: Edexcel IGCSE Chemistry; printable checklist.

Questions

1. Lithium, sodium and potassium are added to separate troughs of water.

(a) State two observations seen with all three metals. [2] (b) Write the balanced equation, with state symbols, for sodium reacting with water. [2] (c) Give one difference in the reactions with water and one in air that show reactivity increases down the group. [2] (d) The melting points of Li, Na and K are 181 °C, 98 °C and 63 °C. Predict the melting point of rubidium. [1]

2. (Paper 2 only) Sodium has the electronic configuration 2.8.1 and potassium 2.8.8.1. Chlorine is 2.8.7; bromine has one more occupied shell than chlorine.

Explain why potassium is more reactive than sodium, but bromine is less reactive than chlorine. [5]

3. This question is about the halogens.

(a) Give the colour and physical state at room temperature of chlorine, bromine and iodine. [3] (b) Predict the state and colour of astatine, below iodine. [1] (c) Bromine water is added to potassium iodide solution and to potassium chloride solution. State what is seen in each tube. [2] (d) Write the balanced equation, with state symbols, for the reaction that occurs. [1]

4. 120 cm³ of air is passed repeatedly over heated copper in a tube joined to two gas syringes. After cooling, 95 cm³ of gas remains.

(a) Calculate the percentage by volume of oxygen in this sample of air. [2] (b) Explain why the air is passed over the copper many times. [1] (c) Explain why the apparatus is cooled before the final reading. [1] (d) Name the most abundant gas in the 95 cm³ and give its approximate percentage by volume in dry air. [1]

5. (a) Describe what is seen when magnesium burns in oxygen, and name the product. [2] (b) Sulfur burns in oxygen. State the flame colour and name the product. [2] (c) Green copper(II) carbonate is heated strongly. State the colour change and write the equation, with state symbols. [2] (d) Explain why rising carbon dioxide levels in the atmosphere are a concern. [1]

6. (a) Give the colour of litmus, phenolphthalein and methyl orange in acid and in alkali. [3] (b) Universal indicator gives these pH values: W 2, X 6, Y 9, Z 12. Classify each solution using the pH scale. [2] (c) Name the ions that acids and alkalis release in water, and write the ionic equation for neutralisation. [2]

7. (Paper 2 only) A student makes pure, dry sodium chloride from hydrochloric acid and sodium hydroxide solution. The titres of acid are 24.60 (rough), 24.15, 24.20 and 24.10 cm³.

(a) Describe how the titration is carried out and how pure, dry crystals are then obtained. [5] (b) Calculate the mean titre using concordant results. [1]

8. (a) Classify each as soluble or insoluble in water: barium sulfate, potassium carbonate, lead(II) chloride, copper(II) nitrate, magnesium hydroxide, ammonium chloride. [3] (b) Ammonia reacts with hydrogen chloride: NH₃ + HCl → NH₄Cl. Identify the acid and the base, in terms of proton transfer. [2] (c) State what is meant by an alkali. [1]

9. Hydrated copper(II) sulfate crystals are made from copper(II) oxide and dilute sulfuric acid.

(a) Write the equation, with state symbols. [1] (b) Describe how to prepare a pure, dry sample of the crystals. [5] (c) Name the salt formed from nitric acid and calcium carbonate, and the other two products. [1]

10. (Paper 2 only) Lead(II) sulfate is made from lead(II) nitrate solution and sodium sulfate solution.

(a) Write the equation, with state symbols. [2] (b) Describe how to obtain a pure, dry sample of lead(II) sulfate. [3]

11. (a) Describe tests, with positive results, for hydrogen, oxygen and chlorine. [3] (b) Describe how to carry out a flame test. [2] (c) Describe a chemical test for water, and a physical test to show the water is pure. [2]

12. Three solids, A, B and C, are tested.

Test	A	B	C
flame test	lilac	no clear colour	no clear colour
solution + sodium hydroxide	no change	green precipitate	no precipitate; on warming, gas turns damp red litmus blue
solution + dilute nitric acid + silver nitrate	yellow precipitate	no change	fizzes; no precipitate
solution + dilute HCl + barium chloride	no change	white precipitate	fizzes; no precipitate

(a) Identify the cation and anion in A and in B. [4] (b) Name the gas given off when C is warmed with sodium hydroxide, and name compound C. Give one further test to confirm the anion in C. [3] (c) Explain why nitric acid, not hydrochloric acid, is used in the silver nitrate test. [1]

Answers

1. (a) Any two: floats; moves around; fizzes; gets smaller and disappears [1] [1]. (b) 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g): formulae and balancing [1]; state symbols [1]. (c) Water: lithium fizzes steadily; sodium melts into a ball; potassium burns with a lilac flame [1]. Air: cut surfaces tarnish faster down the group [1]. (d) About 38 °C (accept 25–50 °C) [1]. [7] Examiner insight: “Fizzes” and “gas given off” are the same point, so they score one mark, not two.

2. Potassium’s outer electron is in a shell further from the nucleus, with more shielding [1]. So it is attracted less strongly and lost more easily [1]. A halogen reacts by gaining an electron [1]. In bromine the outer shell is further from the nucleus [1], so an incoming electron is attracted less strongly and is gained less easily [1]. [5] Examiner insight: “More shells” with no link to weaker attraction scores only the first mark of each chain.

3. (a) Chlorine: green/yellow-green gas [1]. Bromine: red-brown liquid [1]. Iodine: grey-black solid [1]. (b) Black solid [1]. (c) Iodide: turns darker brown (iodine formed) [1]. Chloride: no change (stays orange) [1]. (d) Br₂(aq) + 2KI(aq) → 2KBr(aq) + I₂(aq) [1]. [7] Examiner insight: Each halogen mark needs colour and state; “purple” describes iodine vapour, not the solid.

4. (a) Oxygen used = 120 − 95 = 25 cm³ [1]; 25 ÷ 120 × 100 = 20.8% [1]. (b) So that all the oxygen reacts with the copper [1]. (c) Gases expand when hot, so a warm reading would be too large [1]. (d) Nitrogen, about 78% [1]. [5] Examiner insight: Dividing 25 by 95 gives 26.3% and loses the accuracy mark; use the starting volume.

5. (a) Bright white flame [1]; white powder of magnesium oxide [1]. (b) Blue flame [1]; sulfur dioxide [1]. (c) Green to black [1]; CuCO₃(s) → CuO(s) + CO₂(g) [1]. (d) Carbon dioxide is a greenhouse gas, so more of it may contribute to climate change [1]. [7] Examiner insight: Both colours are needed in (c); “turns black” alone does not score the mark.

6. (a) Litmus: red in acid, blue in alkali [1]. Phenolphthalein: colourless in acid, pink in alkali [1]. Methyl orange: red in acid, yellow in alkali [1]. (b) W strongly acidic, X weakly acidic, Y weakly alkaline, Z strongly alkaline: all four correct [2]; two or three correct scores one mark. (c) Acids: H⁺; alkalis: OH⁻ [1]. H⁺(aq) + OH⁻(aq) → H₂O(l) [1]. [7] Examiner insight: Each indicator mark needs both colours; methyl orange “orange in alkali” is not accepted.

7. (a) Pipette 25.0 cm³ of sodium hydroxide into a conical flask and add a few drops of phenolphthalein or methyl orange [1]. Add acid from a burette, swirling, until the indicator just changes colour; record the volume [1]. Repeat with the same volumes but no indicator [1]. Evaporate some water, then leave to crystallise [1]. Filter and dry the crystals between filter papers [1]. (b) (24.15 + 24.20 + 24.10) ÷ 3 = 24.15 cm³ [1]. [6] Examiner insight: Universal indicator is not credited: its gradual colour change gives no sharp end point.

8. (a) Soluble: potassium carbonate, copper(II) nitrate, ammonium chloride. Insoluble: barium sulfate, lead(II) chloride, magnesium hydroxide. Six correct [3]; four or five, two marks; two or three, one mark. (b) HCl is the acid: it donates a proton [1]. NH₃ is the base: it accepts a proton [1]. (c) A base that is soluble in water [1]. [6] Examiner insight: “Proton” is the key word; “hydrogen” alone is not accepted for H⁺.

9. (a) CuO(s) + H₂SO₄(aq) → CuSO₄(aq) + H₂O(l) [1]. (b) Warm the acid and add copper(II) oxide a little at a time, stirring [1], until some remains unreacted, so all the acid is used [1]. Filter to remove the excess oxide [1]. Evaporate some water from the filtrate, then leave to crystallise [1]. Filter and dry the crystals between filter papers [1]. (c) Calcium nitrate, with water and carbon dioxide [1]. [7] Examiner insight: “Heat to dryness” is not accepted; it drives off the water of crystallisation.

10. (a) Pb(NO₃)₂(aq) + Na₂SO₄(aq) → PbSO₄(s) + 2NaNO₃(aq): formulae and balancing [1]; state symbols, with (s) for lead(II) sulfate [1]. (b) Mix the two solutions to form a precipitate [1]. Filter and wash the precipitate with distilled water [1]. Dry it in a warm oven or between filter papers [1]. [5] Examiner insight: Washing earns its own mark; without it sodium nitrate contaminates the solid.

11. (a) Hydrogen: lighted splint, squeaky pop [1]. Oxygen: relights a glowing splint [1]. Chlorine: bleaches damp litmus paper [1]. (b) Dip a clean wire loop in concentrated hydrochloric acid, then into the solid [1]. Hold it in a blue Bunsen flame; note the colour [1]. (c) Water turns anhydrous copper(II) sulfate from white to blue [1]. Pure water boils at exactly 100 °C (or freezes at 0 °C) [1]. [7] Examiner insight: Glowing splint for oxygen, lighted splint for hydrogen; swapping them loses both marks.

12. (a) A: potassium, K⁺ [1]; iodide, I⁻ [1]. B: iron(II), Fe²⁺ [1]; sulfate, SO₄²⁻ [1]. (b) Ammonia [1]. C is ammonium carbonate [1]. Add dilute hydrochloric acid and bubble the gas through limewater, which turns milky [1]. (c) Chloride ions from hydrochloric acid would give a white precipitate with silver nitrate [1]. [8] Examiner insight: “Iron” without (II) is not credited, because a brown precipitate would show iron(III) instead.

Where marks are usually lost

• Explaining halogen reactivity using electron loss, as for Group 1.
• Dividing by the final gas volume in the oxygen-in-air calculation.
• Using universal indicator in a titration.
• Heating a copper(II) sulfate solution to dryness.
• Not adding excess insoluble reactant, then filtering it off.
• Omitting the washing step when making an insoluble salt.
• Mixing up the glowing splint and lighted splint tests.
• Giving a precipitate result without its colour.

Next steps

• Reactivity and group trends revision notes
• Reactivity and group trends study guide
• Reactivity and group trends practice questions
• Free 4CH1 all-topics diagnostic
• Edexcel IGCSE Chemistry course hub
• Printable Edexcel IGCSE Chemistry checklist
• Book a free trial class

Official syllabus

Pearson Edexcel International GCSE in Chemistry (4CH1) specification, Issue 3, September 2024, published by Pearson Education Limited – Topic 2 Inorganic chemistry, sub-topics (a), (b), (c), (f), (g) and (h).