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Practice paper written from an analysis of every
O-Level Science (Chemistry) paper, 2010–2025
Paper 3 Chemistry
FORECAST PAPER · PAPER 3.4
For practice before the 2026 examination
1 hour 15 minutes
Candidates answer on the Question Paper.
No Additional Materials are required.
Write your name, centre number and index number in the boxes above.
You may use an HB pencil for any diagrams, graphs or rough working.
Write in dark blue or black pen.
Do not use staples, paper clips, glue or correction fluid.
The use of an approved scientific calculator is expected, where appropriate.
You may lose marks if you do not show your working or if you do not use appropriate units.
Section A
Answer all questions.
Write your answers in the spaces provided on the question paper.
Section B
Answer one question.
Write your answers in the spaces provided on the question paper.
A copy of the Data Sheet is printed on page 16.
A copy of the Periodic Table is printed on page 17.
The number of marks is given in brackets [ ] at the end of each question or part question.
The total mark for this paper is 65.
Barium sulfate is an insoluble white solid that patients swallow before an X-ray of the stomach. A technician makes barium sulfate by mixing aqueous barium chloride with aqueous sodium sulfate. A white precipitate forms in the mixture.
The technician separates the solid from the mixture in three steps. The steps are listed below in the wrong order.
step A dry the solid in a warm oven
step B filter the mixture
step C wash the solid with distilled water
Write the letters of the steps in the correct order.
Name the technique used in step B.
Explain why the solid is washed with distilled water in step C.
Fig. 2.1 shows part of the Periodic Table. The letters J, K, L and M show four elements. The number in each box is the proton number. The letters are not the chemical symbols.
Write the electronic configuration of an atom of J.
Which letter, J, K, L or M, shows the element in Group 18?
Which letter, J, K, L or M, shows the element whose atoms have three electron shells and four electrons in the outer shell?
Define the term nucleon number.
Sodium fluoride, NaF, is added to some toothpastes. Fig. 3.1 shows part of the structure of solid sodium fluoride.
Describe how a fluorine atom forms a fluoride ion.
Complete Table 3.1 by writing ‘yes’ or ‘no’ in each empty box.
| state of sodium fluoride | conducts electricity? |
|---|---|
| solid | |
| molten | |
| dissolved in water |
Use Fig. 3.1 to explain the pattern of results in Table 3.1.
Use ideas about ions in your answer.
Brass is an alloy of copper and zinc.
State why brass is classified as a mixture and not as a compound.
Universal Indicator is used to find the pH of some household substances. Table 4.1 shows the pH of four of them.
| substance | pH | colour of Universal Indicator |
|---|---|---|
| tomato juice | 4 | |
| pure water | 7 | green |
| liquid hand soap | 9 | |
| milk of magnesia | 11 | violet |
Complete Table 4.1 to show the colour of Universal Indicator in tomato juice and in liquid hand soap.
Choose from: red, orange, yellow, green, blue, violet.
Milk of magnesia is a white mixture that contains magnesium hydroxide. A student adds milk of magnesia to dilute hydrochloric acid in a beaker.
Complete the word equation for the reaction.
The student adds more milk of magnesia until a piece of Universal Indicator paper placed in the mixture turns green.
State what this shows about the mixture.
Aqueous sodium thiosulfate reacts with dilute hydrochloric acid to form a yellow solid.
A student places a flask containing 50 cm3 of aqueous sodium thiosulfate on a cross marked on paper. 5 cm3 of dilute hydrochloric acid is added and a stopwatch is started. The student looks down through the mixture and stops the stopwatch when the cross can no longer be seen.
The experiment is repeated using aqueous sodium thiosulfate of different concentrations. All other conditions are kept the same. Table 5.1 shows the results.
| experiment | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| concentration of sodium thiosulfate / mol / dm3 | 0.40 | 0.30 | 0.20 | 0.15 |
| time for the cross to disappear / s | 15 | 20 | 30 | 40 |
Plot the results from Table 5.1 on the grid in Fig. 5.1. Draw a smooth curve through the points.
Experiment 5 uses aqueous sodium thiosulfate of concentration 0.25 mol / dm3.
Use your graph to predict the time for the cross to disappear in experiment 5.
Explain why the rate of reaction is higher in experiment 1 than in experiment 4.
Use ideas about particles in your answer.
The student makes the 0.40 mol / dm3 solution by dissolving solid sodium thiosulfate in water. The temperature of the water falls from 24 °C to 20 °C.
State whether dissolving is exothermic or endothermic.
Coal that contains sulfur compounds is the fuel in a power station. Burning it releases sulfur dioxide, SO2, which dissolves in rain water and makes the rain acidic.
Sulfur dioxide is also released into the air from natural sources.
State one natural source of sulfur dioxide.
Acid rain damages statues made from limestone, CaCO3.
Explain why.
State one harmful effect of sulfur dioxide on the health of people.
Some power stations burn bioethanol, a biofuel, instead of coal. Bioethanol is made from the sugar in sugar cane by fermentation.
Complete the word equation for the fermentation of glucose.
Over one year, the sugar cane grown on a farm takes in 118 tonnes of carbon dioxide. Growing the cane, making the bioethanol from it and burning it releases a total of 120 tonnes of carbon dioxide.
Use these data to suggest why bioethanol is more environmentally sustainable than coal.
Fig. 7.1 shows some reactions of the metal P and of its compounds.
Identify each of P, Q, R, S, T, U and V.
You may give the name or the formula of each.
Write a balanced chemical equation, including state symbols, for any one of the reactions shown in Fig. 7.1.
A drain cleaner contains sodium hydroxide. A technician uses a pipette to put 25.0 cm3 of the drain cleaner into a conical flask and adds an indicator. Hydrochloric acid of concentration 0.100 mol / dm3 is added from a burette until the indicator changes colour.
Table 8.1 shows the burette readings for four titrations.
| titration | rough | 1 | 2 | 3 |
|---|---|---|---|---|
| final burette reading / cm3 | 21.30 | 20.60 | 20.20 | 20.00 |
| initial burette reading / cm3 | 0.00 | 0.50 | 0.30 | 0.00 |
| volume of acid added / cm3 |
Complete Table 8.1.
Calculate the mean volume of acid added, using only the results that agree with each other to within 0.20 cm3.
Calculate the amount, in moles, of hydrochloric acid in the volume that you calculated in (b).
Use your answer to (c) and the equation to calculate the amount, in moles, of sodium hydroxide in 25.0 cm3 of the drain cleaner.
Calculate the concentration of sodium hydroxide in the drain cleaner, in mol / dm3.
Calculate the relative formula mass, Mr, of sodium hydroxide.
Use your answers to (e) and (f) to calculate the concentration of sodium hydroxide in the drain cleaner, in g / dm3.
Crude oil is a mixture of hydrocarbons. Fig. 9.1 shows how crude oil is separated into fractions in a fractionating column.
State the boiling range of the fraction that contains molecules with 5 to 9 carbon atoms.
Name the process used to separate the fractions in the column.
Use Fig. 9.1 to describe how the boiling ranges of the fractions change as the number of carbon atoms in the molecules increases.
Describe what is meant by the term hydrocarbon.
The refinery gases include the alkanes methane, ethane and propane.
State the general formula of the alkanes.
Ethane is the second member of the series.
Draw the displayed formula of ethane.
Propane burns completely in oxygen.
Write a balanced chemical equation for this reaction.
Gas J and gas K are butane and butene, but not in this order. Each gas is bubbled through aqueous bromine. Table 9.1 shows the results.
| gas | colour of the aqueous bromine after the gas is bubbled through |
|---|---|
| J | stays orange |
| K | turns colourless |
Fractional distillation of crude oil gives too few small molecules, such as those in petrol, to meet demand.
State why cracking is essential.
The halogens in Group 17 are non-metals. Their molecules contain two atoms.
Fig. 10.1 shows the arrangement of the molecules in samples of chlorine, bromine and iodine at room temperature and pressure.
Identify which diagram, P, Q or R, shows each halogen.
Bromine is obtained from seawater, which contains dissolved sodium bromide. Chlorine gas is bubbled through the seawater and the seawater turns orange. Explain why chlorine displaces bromine from sodium bromide.
Use the Periodic Table to state the number of outer shell electrons in an atom of bromine. Give a reason for your answer.
Table 10.1 shows the observations when aqueous halogens are added to separate samples of two colourless aqueous sodium halides, X and Y. Use data from Table 10.1 to name the sodium halides X and Y.
| aqueous sodium halide | aqueous halogen added | observation |
|---|---|---|
| X | chlorine | the solution turns orange |
| X | iodine | stays brown (no further change) |
| Y | bromine | the solution turns brown |
| Y | chlorine | the solution turns brown |
Aqueous bromine is added to aqueous sodium chloride. Predict whether a reaction occurs. Explain how you made this prediction.
Tetrachloromethane, CCl4, is a covalent compound. Draw a 'dot-and-cross' diagram to show the bonding in a molecule of tetrachloromethane. Show only the outer shell electrons.
Bromine reacts with aqueous sodium iodide. The equation for the reaction is shown.
The metals in Group 1 react with water to form hydrogen.
A student adds a few drops of Universal Indicator to excess water in each of three beakers at the same temperature. The student then adds 0.0020 mol of lithium, 0.0020 mol of sodium and 0.0020 mol of potassium, separately, to the three beakers. The hydrogen produced is collected and its volume is measured at room temperature and pressure. Fig. 11.1 shows the results for the three metals, labelled P, Q and R, but not in this order. The letters are not the chemical symbols.
Use Fig. 11.1 to identify metals P, Q and R.
State the colour of the Universal Indicator in the solution at the end of each experiment.
Lithium and potassium react in a similar way with water. Explain why. Answer in terms of electronic configuration.
Use Fig. 11.1 to describe how the reactivity of the Group 1 metals changes down the group.
Metal Z is in Group 1 and is below potassium in the Periodic Table. The same amount of Z gives 24 cm3 of hydrogen, the same volume as the other three metals. Draw a curve on Fig. 11.1 to show the results you expect when Z is added to excess water under the same conditions. Label the curve Z.
Potassium reacts with sulfur to form potassium sulfide, K2S, an ionic compound. Draw a 'dot-and-cross' diagram to show the bonding in potassium sulfide. Show only the outer shell electrons. Include the charge on each ion.
Potassium reacts with water. The equation for the reaction is shown.
| substance | oxidised | reduced |
|---|---|---|
| potassium | ||
| hydrogen in water |
| aluminium hydroxide | white |
| calcium hydroxide | white |
| copper(II) hydroxide | light blue |
| iron(II) hydroxide | green |
| iron(III) hydroxide | red-brown |
| zinc hydroxide | white |
Group | |||||||||||||||||
1 | 2 |
| 13 | 14 | 15 | 16 | 17 | 18 | |||||||||
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| 1 H hydrogen 1 |
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| 2 He helium 4 | ||
3 Li lithium 7 | 4 Be beryllium 9 |
| proton (atomic) number atomic symbol name relative atomic mass |
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| 5 B boron 11 | 6 C carbon 12 | 7 N nitrogen 14 | 8 O oxygen 16 | 9 F fluorine 19 | 10 Ne neon 20 | ||
11 Na sodium 23 | 12 Mg magnesium 24 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 Al aluminium 27 | 14 Si silicon 28 | 15 P phosphorus 31 | 16 S sulfur 32 | 17 Cl chlorine 35.5 | 18 Ar argon 40 |
19 K potassium 39 | 20 Ca calcium 40 | 21 Sc scandium 45 | 22 Ti titanium 48 | 23 V vanadium 51 | 24 Cr chromium 52 | 25 Mn manganese 55 | 26 Fe iron 56 | 27 Co cobalt 59 | 28 Ni nickel 59 | 29 Cu copper 64 | 30 Zn zinc 65 | 31 Ga gallium 70 | 32 Ge germanium 73 | 33 As arsenic 75 | 34 Se selenium 79 | 35 Br bromine 80 | 36 Kr krypton 84 |
37 Rb rubidium 85 | 38 Sr strontium 88 | 39 Y yttrium 89 | 40 Zr zirconium 91 | 41 Nb niobium 93 | 42 Mo molybdenum 96 | 43 Tc technetium – | 44 Ru ruthenium 101 | 45 Rh rhodium 103 | 46 Pd palladium 106 | 47 Ag silver 108 | 48 Cd cadmium 112 | 49 In indium 115 | 50 Sn tin 119 | 51 Sb antimony 122 | 52 Te tellurium 128 | 53 I iodine 127 | 54 Xe xenon 131 |
55 Cs caesium 133 | 56 Ba barium 137 | 57–71 lanthanoids
| 72 Hf hafnium 178 | 73 Ta tantalum 181 | 74 W tungsten 184 | 75 Re rhenium 186 | 76 Os osmium 190 | 77 Ir iridium 192 | 78 Pt platinum 195 | 79 Au gold 197 | 80 Hg mercury 201 | 81 Tl thallium 204 | 82 Pb lead 207 | 83 Bi bismuth 209 | 84 Po polonium – | 85 At astatine – | 86 Rn radon – |
87 Fr francium – | 88 Ra radium – | 89–103 actinoids
| 104 Rf rutherfordium – | 105 Db dubnium – | 106 Sg seaborgium – | 107 Bh bohrium – | 108 Hs hassium – | 109 Mt meitnerium – | 110 Ds darmstadtium – | 111 Rg roentgenium – | 112 Cn copernicium – | 113 Nh nihonium – | 114 Fl flerovium – | 115 Mc moscovium – | 116 Lv livermorium – | 117 Ts tennessine – | 118 Og oganesson – |
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lanthanoids | 57 La lanthanum 139 | 58 Ce cerium 140 | 59 Pr praseodymium 141 | 60 Nd neodymium 144 | 61 Pm promethium – | 62 Sm samarium 150 | 63 Eu europium 152 | 64 Gd gadolinium 157 | 65 Tb terbium 159 | 66 Dy dysprosium 163 | 67 Ho holmium 165 | 68 Er erbium 167 | 69 Tm thulium 169 | 70 Yb ytterbium 173 | 71 Lu lutetium 175 |
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actinoids | 89 Ac actinium – | 90 Th thorium 232 | 91 Pa protactinium 231 | 92 U uranium 238 | 93 Np neptunium – | 94 Pu plutonium – | 95 Am americium – | 96 Cm curium – | 97 Bk berkelium – | 98 Cf californium – | 99 Es einsteinium – | 100 Fm fermium – | 101 Md mendelevium – | 102 No nobelium – | 103 Lr lawrencium – |
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The volume of one mole of any gas is 24 dm3 at room temperature and pressure (r.t.p.).
The Avogadro constant, L = 6.02 × 1023 mol-1