Use this to mark your own attempt. Accept any correct alternative that answers the question as set. Marks are for the ideas, not the exact words. Unless stated, ecf (error carried forward) applies in calculations. Chermistry practice paper – not an official examination paper.
Total marks: 65 (Section A: 55 marks; Section B: one question of 10 marks)
| Part | Answer and mark points | Marks |
|---|---|---|
| 1(a) | J J has two spots, level with the two spots of G. Reject: K and L (each has a third spot that G does not have). | 1 |
| 1(b) | K K has a spot level with the spot of B. L has three spots but none is level with B. | 1 |
| 1(c) | ink would dissolve in the solvent / ink contains dyes which would also move up the paper (and be separated), so they would interfere with the results / form extra spots Pencil is insoluble in the solvent. Reject: “ink is a different colour”; “pencil is easier to see”. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 2(a) | condensation / condensing (accept: liquefaction / liquefying) Reject: freezing; boiling; evaporation. | 1 |
| 2(b) | in a gas the particles are far apart (large spaces between the particles) so they can be pushed closer together; in a liquid the particles are already close together / touching (no spaces) Both gas and liquid must be described. Reject: the particles in a liquid are heavier / cannot move. | 1 |
| 2(c) | • the particles gain (kinetic) energy / move faster • so they overcome the forces of attraction between them and move far apart / escape from the liquid Reject: the covalent bonds inside the oxygen molecules break; the particles expand. | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 3(a) | the (strong) electrostatic attraction between oppositely charged ions (positive and negative ions) Accept: the attraction between a metal ion and a non-metal ion formed by transfer of electrons. Reject: the sharing of electrons; “the attraction between atoms”. | 1 |
| 3(b) | • giant (ionic) lattice of oppositely charged ions with strong electrostatic forces of attraction between the ions • a lot of energy is needed to overcome these forces / to separate the ions Reject: covalent bonds are broken; “strong ionic bonds between molecules”. | 2 |
| 3(c) | sulfur is made of (neutral) molecules / it has no ions and no free electrons, so there are no charged particles that are free to move Reject: “it has covalent bonds” with no reference to charged particles; “the electrons cannot move” without reference to there being no ions. | 1 |
| 3(d) | • solid does not conduct and molten conducts • it is an ionic compound (metal + non-metal): the ions cannot move in the solid, but are free to move when molten The second mark needs the idea of ions that are fixed (solid) / free to move (molten). Reject: electrons carry the current. | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 4(a) | the pH decreases (steadily) as time increases / the solution becomes more acidic Reject: “it changes” or “it increases”. | 1 |
| 4(b) | day 14 Reject: day 7 (pH 5.9 is inside the range); day 21 or 28. | 1 |
| 4(c) | potassium nitrate (accept KNO3) Reject: potassium nitrite; potassium hydroxide nitrate; water on its own. | 1 |
| 4(d) | • pH between 3.4 and 3.8 (3.6) [1] • the pH has been falling by about 0.6 each week (every 7 days) in the last two weeks, so it falls by about 0.6 from 4.2 [1] • Accept a value from 3.4 to 3.8. Also accept 3.9–4.1 with a data-based reason: 1 mark for the reason only. The reason must refer to the pattern in the data, e.g. “it falls by about 0.5–0.6 each week”. Reject: a value of 4.2 or above; a reason with no data. | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 5(a) | 36 ÷ 30 = 1.2 cm3 / s The unit must be correct (cm3 per second). | 1 |
| 5(b) | experiment 1 (iron powder) and more hydrogen is collected in the same time (e.g. 36 cm3 against 12 cm3 in 30 s) Reject: the name or number of the experiment without a reason from the data. | 1 |
| 5(c) | • powder has a larger surface area (more iron atoms exposed to the acid) • so the acid particles collide more frequently with the iron / there are more collisions per second (higher collision frequency) Reject: the particles have more energy / move faster; “more collisions” without a time idea (“more frequent”, “per second”). | 2 |
| 5(d) | exothermic Accept: heat is given out to the surroundings. Reject: endothermic. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 6(a) | • carbon monoxide: incomplete combustion of fuels containing carbon and toxic (reduces the oxygen carried by the blood) • methane: decay of rubbish and animal waste and greenhouse gas (causes global warming) • sulfur dioxide: burning fuels that contain sulfur and dissolves in rain water to form acid rain • 1 mark for each gas with both lines correct. A gas with two lines to the same side, or more than one line to a source or effect, scores 0. The lightning and photosynthesis items are distractors and are not joined. | 3 |
| 6(b) | • It is made by fermenting the sugar in sugar cane. [1] • It can be burnt as a fuel in engines. [1] • (Natural gas is mainly methane; petrol and diesel, not bioethanol, come from crude oil; ethanol contains oxygen, so it is not a hydrocarbon.) • If more than two boxes are ticked, subtract 1 mark for each extra tick (minimum 0). | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 7(a) | • add aqueous sodium hydroxide to a sample of each solution, a little at a time and then in excess; ammonium nitrate gives no precipitate, and on warming the gas given off turns damp red litmus paper blue (ammonia) [1] • zinc sulfate and aluminium nitrate each give a white precipitate that dissolves in excess aqueous sodium hydroxide (so they cannot be told apart with sodium hydroxide) [1] • add aqueous ammonia, a little at a time and then in excess, to samples of these two solutions [1 for the method] • zinc sulfate: the white precipitate dissolves in excess aqueous ammonia; aluminium nitrate: the white precipitate does not dissolve in excess [1] • Alternative order accepted if every solution is identified from clear results. Accept the formulae. Reject: “a precipitate forms” with no colour. | 4 |
| 7(b) | both give a white precipitate that dissolves in excess aqueous sodium hydroxide (to give a colourless solution) Reject: “the precipitates are the same colour” with no reference to dissolving in excess. | 1 |
| 7(c) | • S is barium sulfate (accept BaSO4) [1] • the anion in R is sulfate (accept SO42−) [1] • Reject: barium nitrate or barium carbonate for S; sulfite; sulfide; carbonate (no gas is given off with dilute hydrochloric acid). R is sodium sulfate. | 2 |
| 7(d) | • correct formulae of all reactants and products: Na2SO4, Ba(NO3)2, BaSO4, NaNO3 [1]; balanced [1]; correct state symbols [1] • Na2SO4(aq) + Ba(NO3)2(aq) → BaSO4(s) + 2NaNO3(aq) • Accept the ionic equation Ba2+(aq) + SO42−(aq) → BaSO4(s). Correct formulae but unbalanced: 1 mark. Missing or wrong state symbols lose only the third mark. A wrong formula for R loses the formulae mark; ecf for balancing and state symbols. | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 8(a) | (2 × 14) + 16 = 44 | 1 |
| 8(b) | NH4NO3: Mr = 14 + 4 + 14 + 48 = 80; 2.0 kg = 2000 g; 2000 ÷ 80 = 25 mol Using 2.0 g instead of 2000 g: 0 marks. | 1 |
| 8(c) | 1 mol ammonium nitrate gives 1 mol dinitrogen oxide, so 25 mol [1]; 25 × 24 = 600 dm3 [1] (ecf from (b)) | 2 |
| 8(d) | 25 × 44 = 1100 g (ecf from (a) and (b)) Accept 1.1 kg. | 1 |
| 8(e) | 500 cm3 = 0.500 dm3; 0.200 × 0.500 = 0.100 mol [1]; 0.100 × 80 = 8.0 g [1] (ecf for the second mark) | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 9(a) | One carbon atom with three C–H bonds and one C–O bond; the O bonded to one H; every bond drawn. | 1 |
| 9(b) | C2H6O (accept C2H5OH or CH3CH2OH) Reject: CH3OH; C2H5O. | 1 |
| 9(c) | • step 1: the beaker is open to the air, so ethanol would be oxidised to ethanoic acid (the mixture turns sour) / oxygen must be kept out; use a closed flask with an air lock (or a bung and delivery tube) [1] • step 2: 80 °C is too hot, it kills the yeast (the enzymes in the yeast stop working); keep the mixture warm at about 30–40 °C [1] • step 3: the mixture contains mostly water (and yeast and other substances), so it is not ethanol; separate the ethanol by (fractional) distillation [1] • Each mistake needs its correction for the mark. Accept 25–45 °C. Reject: “the time is too long”; “heat to 100 °C”; “add more yeast”. | 3 |
| 9(d) | C6H12O6 → 2C2H5OH + 2CO2 Accept state symbols; C2H6O or CH3CH2OH for ethanol. Reject an unbalanced equation. | 1 |
| 9(e) | any two from: carbon monoxide; water; carbon (soot) Accept the formulae CO, H2O, C. Reject: oxygen; hydrogen; carbon dioxide. | 2 |
| 9(f) | • unsaturated: (the molecule) contains a carbon–carbon double bond (C=C) • addition (reaction) (accept: the bromine / hydrogen atoms add across the C=C double bond) Reject: “has a double bond” with no mention of carbon; “contains double bonds between hydrogen atoms”; substitution; combustion; polymerisation (not with bromine or hydrogen). | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 10(a) | • E is a solid (it is below the liquid C: the states change from gas to liquid to solid down the group) • Cl2 (accept B2; halogens are diatomic: a molecule of B has two atoms) • KI (accept KD; potassium forms an ionic compound with D: one K+ ion to one D− ion) • all three correct = 2 marks; two correct = 1 mark; one or none = 0. Reject: Cl; Cl2; K2I; liquid; gas. Accept IK and DK. | 2 |
| 10(b) | • B (potassium ions, chloride ions and iodine molecules, I2: Cl2 + 2KI → 2KCl + I2). A: no reaction; C: iodine shown as single atoms (iodine exists as I2 molecules); D: the iodide ions have not reacted and the charges do not balance. | 1 |
| 10(c) | • two crosses on the first shell, eight on the second shell and seven on the third shell (2.8.7). All three shells correct for the mark. Accept crosses, dots or any consistent symbol; accept electrons not evenly spaced. Reject: any shell with the wrong number. | 1 |
| 10(d) | the colour gets darker (down the group). Accept: pale yellow, pale green, red-brown, grey-black in that order; deeper / more intense colour. Reject: ‘changes colour’ or ‘becomes lighter’; a description of the state only. | 1 |
| 10(e)(i) | black (accept very dark / dark grey / grey-black / darker than iodine). Reject: any pale colour (yellow, green, brown, red-brown, purple); silver; white; colourless. | 1 |
| 10(e)(ii) | seven (7) and a reason: astatine is in Group 17, so it has the same number of outer shell electrons as the other halogens (fluorine 2.7 and chlorine 2.8.7 have seven). Both the number and the reason are needed. Reject: 85; eight; 17; ‘because it is a halogen’ with no reference to the group or to the other halogens. | 1 |
| 10(f) | • 2 electrons on the inner shell of each atom (4 in all) and one shared pair (one dot and one cross) in the overlap • three non-bonding pairs (lone pairs) on each atom, so eight electrons in the outer shell of each atom, including the shared pair (18 electrons in all) • Accept all electrons as dots or all as crosses if the single bond is clear. Do not credit: ions drawn; a double bond; inner shells left empty (the first mark is not awarded); seven electrons around either atom. | 2 |
| 10(g) | from 0 to −1. Both values are needed. Accept: decreases from 0 to −1. Reject: −1 to 0; 0 to +1; "decreases" with no values. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 11(a) | • any two different variables from: mass (or size / surface area / form) of the metal; volume of the acid; concentration of the acid; temperature (of the acid) • one mark each. Accept: ‘same amount (mass) of metal’. Reject: same apparatus / same gas syringe; time (it is measured); the type of metal; the volume of hydrogen; ‘amount of acid’ with no volume or concentration; pressure. | 2 |
| 11(b) | 8 ÷ 20 = 0.40 (accept 0.4 / 0.40; the unit is printed). Reject: 2.5 (20 ÷ 8); 0.30 (18 ÷ 60); 0.7 (14 ÷ 20). | 1 |
| 11(c) | magnesium, zinc, iron (all three in this order). Accept symbols Mg, Zn, Fe. Reject: any other order. (The larger the rate, the more reactive: 1.9 > 0.40 > 0.15.) Allow ecf from (b) if the order is consistent with the student’s own value. | 1 |
| 11(d) | copper is below hydrogen / copper is less reactive than hydrogen. Accept: copper is below iron, zinc and magnesium and below hydrogen. Reject: ‘copper is unreactive’ with no comparison; above hydrogen; ‘copper does not react’ alone. | 1 |
| 11(e)(i) | repeat the experiment (at least twice more) and calculate the mean / average (for each metal). Accept: repeat the experiment and compare the results / discard anomalous results and average. Reject: use a more accurate gas syringe (not reliability); use more acid; ‘repeat the experiment’ with no mention of comparing or averaging the results. | 1 |
| 11(e)(ii) | any value from 10 to 13 cm3 (the best estimate is about 11 cm3, halfway between the readings at 20 s and 40 s). Unit not required. Reject: 8 or 14 (the readings at 20 s and 40 s); any value outside 10–13; 18 (the reading at 60 s); 0.40. | 1 |
| 11(f) | • 1 mark: charge 2+ on the magnesium ion, with no electrons shown or with 8 electrons in its outer shell (both accepted) • 1 mark: one cross added to each chloride ion (eight outer electrons) and the charge − on each chloride ion • Accept: all electrons as dots or all as crosses if the transfer is clear. Do not credit: shared pairs (covalent bonding); a missing or wrong charge loses that mark. | 2 |
| 11(g) | iron atoms lose electrons (two electrons each, to form Fe2+ ions). Accept: electrons are transferred from iron to hydrogen ions; the oxidation state of iron increases from 0 to +2. Reject: ‘loses electrons’ with no species named; iron gains electrons; ‘gains oxygen’. | 1 |