How to Use This Worksheet
Work in order. Section A checks the five patterns, the three reaction families, and the activity series. Section B practises predicting products: replacements that do or do not run, cation swaps, a carbonate fizzing, and two reactions carried through with numbers. Section C combines classification, prediction and electron transfer in exam style.
Two reference sets are used throughout. The activity series, most reactive first, runs: potassium, sodium, calcium, magnesium, aluminium, zinc, iron, lead, hydrogen, copper, silver, gold. A free element displaces only elements below it. The solubility anchors are: BaSO₄, CaCO₃, AgCl and PbI₂ are insoluble; all nitrates, and all sodium and potassium salts, are soluble.
Molar masses you need: Mg 24.31 g/mol, H₂ 2.02 g/mol, C₃H₈ 44.10 g/mol, CO₂ 44.01 g/mol, H₂O 18.02 g/mol, O₂ 32.00 g/mol, BaSO₄ 233.39 g/mol. The molar volume of a gas at STP is 22.4 L/mol. Carry unrounded values through each calculation and round only the final answer, to three significant figures.
Classify with both systems every time: first the pattern (synthesis, decomposition, single replacement, double replacement, combustion), then the family (acid-base, precipitation, redox). Many reactions take one label from each.
Do not look at the answer key until you have attempted every question.
Section A: Recall and Concepts
A1. For each pattern, state the general form and give one example equation.
(a) Synthesis.
(b) Decomposition.
(c) Single replacement.
(d) Double replacement.
(e) Combustion of a hydrocarbon in excess oxygen.
A2. Define each term in one sentence.
(a) Activity series.
(b) Redox reaction.
(c) Precipitation reaction.
(d) Neutralisation.
(e) Complete combustion.
A3. For each reaction, state which substance is oxidised and which is reduced, or state that the reaction is not redox.
(a) Zn + CuSO₄ → ZnSO₄ + Cu
(b) Cl₂ + 2NaBr → 2NaCl + Br₂
(c) HCl + NaOH → NaCl + H₂O
(d) 2Mg + O₂ → 2MgO
A4. Using the activity series in the introduction, state whether each single replacement reaction occurs. Where it does, write the balanced equation.
(a) Copper metal is placed in zinc sulfate solution.
(b) Zinc metal is placed in copper(II) sulfate solution.
(c) Iron metal is placed in dilute hydrochloric acid.
(d) Copper metal is placed in dilute hydrochloric acid.
(e) Silver metal is placed in copper(II) nitrate solution.
A5. Complete and balance each equation.
(a) __ Na + __ Cl₂ → __ NaCl
(b) __ H₂O₂ → __ H₂O + __ O₂
(c) __ C₂H₆ + __ O₂ → __ CO₂ + __ H₂O
(d) __ KClO₃ → __ KCl + __ O₂
Section B: Core Practice
B1. Classify each reaction, giving every label that applies: the pattern, and the family where one applies.
(a) CaCO₃ → CaO + CO₂
(b) BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl
(c) HCl + NaOH → NaCl + H₂O
(d) Zn + 2HCl → ZnCl₂ + H₂
(e) C₃H₈ + 5O₂ → 3CO₂ + 4H₂O
(f) CaO + H₂O → Ca(OH)₂
B2. Magnesium ribbon is dropped into dilute hydrochloric acid and fizzes vigorously.
(a) State the pattern of this reaction and write the balanced equation.
(b) Calculate the moles of magnesium in 2.43 g of the metal.
(c) Calculate the volume of hydrogen gas, measured at STP, that this mass of magnesium produces.
(d) State which species is oxidised and which is reduced.
(e) The flask stands on a balance throughout. Predict how the total mass of the flask and its contents changes as the magnesium reacts, and calculate that change.
B3. Predict the products of each double replacement. Write the balanced equation where a reaction occurs, and explain your decision each time.
(a) Lead(II) nitrate solution is mixed with potassium iodide solution.
(b) Calcium chloride solution is mixed with sodium carbonate solution.
(c) Sodium chloride solution is mixed with potassium nitrate solution.
B4. A student adds dilute hydrochloric acid to solid calcium carbonate and sees fizzing.
(a) Write the balanced equation for the reaction.
(b) Name all three products.
(c) Classify the reaction, giving a pattern label and a family label.
(d) Explain what the fizzing is, and why it shows a chemical change rather than a physical one.
(e) The student repeats the experiment with the flask sealed and standing on a balance. State what happens to the balance reading this time, and explain the difference from the open flask in terms of where the atoms go.
B5. A camping stove burns propane, C₃H₈, in excess oxygen.
(a) Calculate the moles of propane in 4.41 g.
(b) Write the balanced equation for the complete combustion, and calculate the moles and the mass of oxygen used.
(c) Calculate the masses of carbon dioxide and water formed.
(d) Use your answers to show that mass is conserved in this reaction.
(e) The stove is then run with its air inlet partly closed, so oxygen is in limited supply. State how the products change, and whether the mass of carbon dioxide formed from 4.41 g of propane rises, falls, or stays the same.
B6. A solution containing 0.0100 mol of BaCl₂ is mixed with excess sodium sulfate solution.
(a) Write the balanced equation for the reaction.
(b) Classify the reaction, giving a pattern label and a family label.
(c) Calculate the mass of BaSO₄ precipitated.
(d) State which two ions remain dissolved and unchanged.
(e) The precipitate is filtered off, washed and dried before weighing. Give two reasons why the mass collected is likely to be slightly less than the value you calculated in part (c).
Section C: Exam Style
C1. A student places a piece of zinc metal in copper(II) sulfate solution. The blue colour of the solution slowly fades, a brown solid forms on the zinc, and the temperature of the solution rises.
(a) Write the balanced equation for the reaction.
(b) Give two classifications for this reaction, justifying each in one sentence.
(c) State the oxidation number change for zinc and for copper, and hence state which species is oxidised and which is reduced.
(d) Explain, in terms of the particles present, why the blue colour fades.
(e) The student then places a piece of copper metal in zinc sulfate solution. Predict what is observed and explain your prediction.
C2. A student tries to write the reaction between aluminium and copper(II) sulfate and produces: Al + CuSO₄ → AlSO₄ + Cu.
(a) Explain, using ion charges, why the product formula AlSO₄ is impossible, and state the correct formula for aluminium sulfate.
(b) Write the correctly balanced equation for the reaction.
(c) State whether the reaction occurs, justifying your answer with the activity series, and give one observation that would be seen.
C3. For each mixture, state whether a reaction occurs. Where it does, write the balanced equation and give one classification label. Where it does not, explain why not.
(a) An iron nail is left standing in copper(II) sulfate solution.
(b) A copper strip is left standing in zinc sulfate solution.
(c) Dilute hydrochloric acid is poured onto sodium carbonate solution.
(d) Silver nitrate solution is mixed with potassium chloride solution.
(e) Sodium chloride solution is mixed with potassium nitrate solution.
Show the answer key and full working (only after you have attempted every question)
A1. (a) A + B → AB: two or more reactants combine into one product, e.g. 2Mg + O₂ → 2MgO. (b) AB → A + B: one reactant splits into two or more products, e.g. CaCO₃ → CaO + CO₂. (c) A + BC → AC + B: a free element displaces another element from its compound, e.g. Zn + CuSO₄ → ZnSO₄ + Cu. (d) AB + CD → AD + CB: two compounds exchange ions, e.g. AgNO₃ + NaCl → AgCl + NaNO₃. (e) Hydrocarbon + O₂ → CO₂ + H₂O, e.g. CH₄ + 2O₂ → CO₂ + 2H₂O.
A2. (a) The ranking of elements by reactivity: a free element displaces only elements ranked below it from their compounds. (b) A reaction in which electrons are transferred, so oxidation numbers change: one substance loses electrons and is oxidised, another gains them and is reduced. (c) A reaction in solution in which ions combine to form an insoluble solid that leaves the solution as a precipitate. (d) The reaction of an acid with a base to form a salt and water. (e) The burning of a fuel in excess oxygen, so that every carbon atom forms CO₂ and every hydrogen atom forms H₂O.
A3. (a) Zinc is oxidised (0 to +2, losing electrons); copper(II) ions are reduced (+2 to 0, gaining electrons). (b) Chlorine is reduced (0 to −1, gaining electrons); bromide ions are oxidised (−1 to 0, losing electrons). (c) Not redox: hydrogen stays at +1, oxygen at −2, sodium at +1 and chlorine at −1 throughout; it is an acid-base reaction. (d) Magnesium is oxidised (0 to +2); oxygen is reduced (0 to −2).
A4. (a) No reaction: copper is below zinc in the series, so it cannot displace zinc. (b) Reaction: Zn + CuSO₄ → ZnSO₄ + Cu. Zinc is above copper. (c) Reaction: Fe + 2HCl → FeCl₂ + H₂. Iron is above hydrogen, so it displaces hydrogen from the acid. (d) No reaction: copper is below hydrogen, so it cannot displace hydrogen from the acid. (e) No reaction: silver is below copper in the series.
A5. (a) 2Na + Cl₂ → 2NaCl. (b) 2H₂O₂ → 2H₂O + O₂. (c) 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O. (d) 2KClO₃ → 2KCl + 3O₂.
B1. (a) Decomposition. Oxidation numbers do not change (Ca +2, C +4, O −2 throughout), so no family label applies. (b) Double replacement, and precipitation: the cations swap partners and BaSO₄ is insoluble. (c) Double replacement, and acid-base (neutralisation): a salt and water form, with no oxidation number changes. (d) Single replacement, and redox: zinc (0 to +2) displaces hydrogen (+1 to 0). (e) Combustion, and redox: carbon and hydrogen are oxidised and oxygen is reduced. (f) Synthesis: two compounds join into one product, with no oxidation number changes.
B2. (a) Single replacement: magnesium sits above hydrogen in the activity series and displaces it. Mg + 2HCl → MgCl₂ + H₂. (b) Moles of Mg = 2.43 ÷ 24.31 = 0.100 mol. (c) The equation ratio is 1 : 1, so moles of H₂ = 0.100 mol. Volume at STP = 0.100 × 22.4 = 2.24 L. (d) Magnesium is oxidised (0 to +2 in Mg²⁺); hydrogen ions are reduced (+1 to 0 in H₂). (e) The total mass falls, by the mass of the hydrogen that escapes as a gas: 0.100 × 2.02 = 0.202 g. Equivalently, the solution itself gains 2.43 − 0.202 = 2.23 g, because the magnesium’s mass joins it as Mg²⁺ while the hydrogen bubbles away.
B3. (a) Swap the cations: Pb²⁺ pairs with I⁻ and K⁺ pairs with NO₃⁻. PbI₂ is insoluble, so the reaction occurs: Pb(NO₃)₂ + 2KI → PbI₂ + 2KNO₃, forming a yellow precipitate. (b) Swap the cations: Ca²⁺ pairs with CO₃²⁻ and Na⁺ pairs with Cl⁻. CaCO₃ is insoluble, so the reaction occurs: CaCl₂ + Na₂CO₃ → CaCO₃ + 2NaCl, forming a white precipitate. (c) The swap would give NaNO₃ and KCl, but both are soluble; no precipitate, gas or water forms, so all four ions stay dissolved and no reaction occurs.
B4. (a) CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂. (b) Calcium chloride (the salt, dissolved in the water present), water, and carbon dioxide. (c) Pattern: double replacement, the calcium and hydrogen cations exchanging partners. Family: acid-base, an acid reacting with a carbonate base; it is also gas-forming. (d) The fizzing is carbon dioxide gas being produced and escaping. It shows a chemical change because a new substance, the gas, is being formed from the reactants; the bubbles are not the liquid boiling, because no heating is applied and the gas is a different substance from anything that was present before. (e) The reading stays constant. In the sealed flask the CO₂ cannot escape, so every atom that was present at the start is still inside at the end, only rearranged into new substances. In the open flask the reading falls because the CO₂ leaves, carrying its mass away with it.
B5. (a) Moles of C₃H₈ = 4.41 ÷ 44.10 = 0.100 mol. (b) C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. Moles of O₂ = 5 × 0.100 = 0.500 mol; mass = 0.500 × 32.00 = 16.0 g. (c) Moles of CO₂ = 3 × 0.100 = 0.300 mol, mass = 0.300 × 44.01 = 13.2 g. Moles of H₂O = 4 × 0.100 = 0.400 mol, mass = 0.400 × 18.02 = 7.21 g. (d) Mass of reactants = 4.41 + 16.0 = 20.4 g. Mass of products = 13.2 + 7.21 = 20.4 g, to three significant figures. The totals agree, so mass is conserved, as it must be when every atom in the reactants appears in the products. (e) With oxygen limited, the combustion is incomplete: some carbon forms carbon monoxide or soot (carbon) instead of CO₂, so the mass of CO₂ from 4.41 g of propane falls. Less of the propane’s carbon reaches CO₂, even though mass overall is still conserved.
B6. (a) BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl. (b) Pattern: double replacement. Family: precipitation, because BaSO₄ is insoluble and leaves the solution as a solid. (c) The equation ratio is 1 : 1, so moles of BaSO₄ = 0.0100 mol. Mass = 0.0100 × 233.39 = 2.33 g. (d) Na⁺ and Cl⁻: they appear unchanged on both sides of the equation and take no part in forming the solid. (e) Any two of: a little BaSO₄ remains stuck to the beaker, stirrer and filter paper during transfer; some very fine particles pass through the filter paper; a trace of BaSO₄ stays dissolved, because no solid is completely insoluble; some solid is lost when the filter paper is handled and dried.
C1. (a) Zn + CuSO₄ → ZnSO₄ + Cu. (b) Single replacement, because the free element zinc takes the place of copper in its compound; and redox, because electrons are transferred, zinc atoms becoming Zn²⁺ ions while Cu²⁺ ions become copper atoms. (c) Zinc: 0 to +2, so zinc is oxidised. Copper: +2 to 0, so copper(II) ions are reduced. (d) The blue colour belongs to Cu²⁺ ions in solution. As the reaction proceeds those ions are converted into copper metal on the surface of the zinc, so their concentration falls and the colour fades; the Zn²⁺ ions replacing them are colourless. (e) Nothing is observed: the solution stays blue and the copper is unchanged. Copper is below zinc in the activity series, so it cannot displace zinc from its compound.
C2. (a) Aluminium forms Al³⁺ ions and sulfate is SO₄²⁻. In AlSO₄ the total charge would be +3 + (−2) = +1, not zero, and an ionic compound must be neutral overall. Two Al³⁺ ions (+6) balance three SO₄²⁻ ions (−6), so the correct formula is Al₂(SO₄)₃. (b) 2Al + 3CuSO₄ → Al₂(SO₄)₃ + 3Cu. (c) The reaction occurs: aluminium is above copper in the activity series, so it displaces copper from its salt. The blue colour of the solution fades as Cu²⁺ leaves it, and a brown coating of copper forms on the aluminium.
C3. (a) Reaction: Fe + CuSO₄ → FeSO₄ + Cu. Single replacement (also redox): iron is above copper in the activity series. (b) No reaction: copper is below zinc, so it cannot displace zinc from zinc sulfate. (c) Reaction: 2HCl + Na₂CO₃ → 2NaCl + H₂O + CO₂. Acid-base: the acid reacts with the carbonate to give a salt, water and carbon dioxide, seen as effervescence. (d) Reaction: AgNO₃ + KCl → AgCl + KNO₃. Double replacement (also precipitation): AgCl is insoluble and forms a white precipitate. (e) No reaction: swapping the cations would give NaNO₃ and KCl, both soluble, and no gas or water forms, so every ion remains dissolved.