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) | A and ammonia is less dense than air, so it rises and pushes the air out of the bottom of the inverted tube (upward delivery = downward displacement of air) Accept: ammonia dissolves in water, so B is not suitable. Reject: the letter with no reason; C (a gas syringe measures a volume; it is not used to collect a sample in a tube). | 1 |
| 1(b) | C and the gas does not come into contact with water, so it does not dissolve / the volume of gas is read from the scale on the syringe Reject: the letter with no reason; B (sulfur dioxide would dissolve in the water). | 1 |
| 1(c) | B and carbon monoxide does not dissolve in water / its density is too close to that of air for A to separate it from the air Reject: the letter with no reason; A (the gas would mix with the air). | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 2(a) | neutron: relative charge 0 [1]; electron: relative mass 1/1840 [1] Accept for the electron: 1/1836; 1/2000; 0.0005; negligible; almost zero. Reject: 0 for the electron mass; “−1” for the neutron charge. | 2 |
| 2(b) | 1 (3 − 2 = 1) | 1 |
| 2(c) | 2 (an atom has the same number of electrons as protons) | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 3(a) | A element [1]; B compound [1]; C mixture [1] | 3 |
| 3(b) | • each aluminium atom loses three electrons • so that the ion has the (stable) electronic configuration of a noble gas / a full outer shell (that of neon) • Reject: gains electrons; “shares” electrons; the loss of protons or neutrons. | 2 |
| 3(c) | good conductor of electricity / good conductor of heat / malleable / high melting point / high boiling point Accept: ductile; shiny / lustrous. Reject: hard; strong; dense; unreactive; “conducts” alone. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 4(a) | A (equal numbers of H+ and OH− ions) | 1 |
| 4(b) | C (more OH− ions than H+ ions) | 1 |
| 4(c) | B (the highest concentration of H+ ions) | 1 |
| 4(d) | equal numbers of H+ and OH− ions drawn, with at least one of each Accept any equal numbers (at least one of each). Reject: unequal numbers; only one kind of ion; a beaker with no ions. | 1 |
| 4(e) | hydrogen Accept: H2. Reject: oxygen; carbon dioxide. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 5(a) | 120 cm3 (the reaction with small chips has finished, so the volume no longer changes) Reject: any value other than 120. | 1 |
| 5(b) | • small chips have a larger surface area (more calcium carbonate particles are exposed to the acid) • so the acid particles collide with the calcium carbonate particles more frequently (higher collision frequency) • Reject: “more particles” or “more collisions” without frequent / per second; “particles have more energy”; “higher temperature”. | 2 |
| 5(c) | the volume of gas in the syringe stops increasing / the reading on the syringe stays the same Accept: the plunger stops moving; no more bubbles of gas are made; the fizzing stops; no marble chips left / all the marble has dissolved. Reject: the colour changes; the temperature stops changing. | 1 |
| 5(d) | exothermic and the temperature increases / heat energy is given out to the surroundings Reject: endothermic; a reason with no type of reaction. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 6(a) | correct (no correction needed) | 1 |
| 6(b) | not correct and any ONE of: methane would otherwise escape into the air and is a greenhouse gas; the carbon dioxide formed is offset by the carbon dioxide taken in by plants (photosynthesis); collecting / burning biogas helps to reduce global warming | 1 |
| 6(c) | not correct and photosynthesis removes carbon dioxide from the air (bracket optional: respiration, combustion and decay add it) | 1 |
| 6(d) | correct (no correction needed) | 1 |
| 6(e) | not correct and burning biogas releases carbon dioxide (accepted extra, not required: the plants that formed the waste took in the same amount of carbon dioxide by photosynthesis, so it offsets) | 1 |
| Part | Answer and mark points | Marks | |||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 7(a) |
| 7 | |||||||||||||||||||||
| 7(b) | • correct formulae of all reactants and products [1]; balanced [1]; correct state symbols [1] • Missing or incorrect state symbols: lose the third mark only. Correct formulae but unbalanced: 1 mark. Any wrong formula: 0 for the formulae mark and 0 for balancing. • Fe2O3(s) + 6HCl(aq) → 2FeCl3(aq) + 3H2O(l) • or FeCl3(aq) + 3NaOH(aq) → Fe(OH)3(s) + 3NaCl(aq) (ionic: Fe3+(aq) + 3OH−(aq) → Fe(OH)3(s)) • or FeCl3(aq) + 3AgNO3(aq) → 3AgCl(s) + Fe(NO3)3(aq) (ionic: Ag+(aq) + Cl−(aq) → AgCl(s)) • or Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 8(a) | 14 + (4 × 1) + 35.5 = 53.5 | 1 |
| 8(b) | 4.28 ÷ 53.5 = 0.0800 mol (ecf from (a)) | 1 |
| 8(c) | 2 mol NH4Cl react with 1 mol Ca(OH)2: 0.0800 ÷ 2 = 0.0400 mol [1]; Mr of Ca(OH)2 = 40 + 2(16 + 1) = 74; 0.0400 × 74 = 2.96 g [1] (ecf from (b)) | 2 |
| 8(d) | 2 mol NH4Cl form 2 mol NH3, so 0.0800 mol NH3; 0.0800 × 24 = 1.92 dm3 (ecf from (b)) | 1 |
| 8(e) | 500 cm3 = 0.500 dm3; 0.0800 ÷ 0.500 = 0.160 mol / dm3 (accept 0.16) (ecf from (b)) | 1 |
| 8(f) | Mr of NH3 = 14 + 3 = 17; 0.160 × 17 = 2.72 g / dm3 (accept 2.7) (ecf from (e)) | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 9(a) | ethanol: C2H5OH [1]; propanol [1] Accept: C2H6O or CH3CH2OH; propan-1-ol or propan-2-ol. | 2 |
| 9(b) | Three carbon atoms in a chain, each with four bonds; the O–H group on the end carbon atom; every bond drawn, including C–H and O–H. Also accept propan-2-ol (OH on the middle carbon atom), as it also has the formula C3H7OH. Reject: a missing bond or atom; a C–O–C (ether) chain; a branched or four-carbon chain. | 1 |
| 9(c) | the boiling point increases (gradually) as the number of carbon atoms increases Reject: decreases; “gets higher” with no link to the number of carbon atoms. | 1 |
| 9(d) | C2H5OH + 3O2 → 2CO2 + 3H2O Accept: C2H6O or CH3CH2OH; state symbols (not required). Reject: an unbalanced equation; carbon monoxide as a product. | 1 |
| 9(e) | acidified potassium manganate(VII) (accept: acidified KMnO4; oxygen from the air / atmospheric oxygen) Acidified potassium dichromate(VI) is not in the syllabus but is correct chemistry: do not penalise it. Reject: potassium manganate(VII) with no acid; hydrogen; reducing agents. | 1 |
| 9(f) | ethanoic acid Accept: acetic acid; CH3CO2H or CH3COOH. Reject: ethanol; methanoic acid; propanoic acid. | 1 |
| 9(g)(i) | sunflower oil and it decolourises the largest volume of aqueous bromine (7.5 cm3) Reject: the name alone; “coconut oil” (it decolourises the smallest volume, so it is the least unsaturated). | 1 |
| 9(g)(ii) | the oil molecules contain C=C double bonds, which react with (add) bromine / bromine adds across the C=C double bond Reject: “it has a double bond” with no link to reacting with bromine; bromine is oxidised; hydrogen. | 1 |
| 9(h) | C A is poly(ethene); B still has a C=C double bond; D has a CN group on both carbon atoms. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 10(a) | • calcium, cold water: bubbles; calcium, dilute hydrochloric acid: bubbles • iron, dilute hydrochloric acid: bubbles; copper, dilute hydrochloric acid: no bubbles • All four correct = 2 marks; two or three correct = 1 mark; fewer than two correct = 0. Accept "reacts / no reaction" for bubbles / no bubbles. | 2 |
| 10(b) | calcium and iron (accept: more reactive than iron but less reactive than calcium). Reject: sodium and calcium; iron and copper. | 1 |
| 10(c) | iron. (Calcium, magnesium and sodium are more reactive than carbon, so carbon cannot remove oxygen from their oxides; iron is less reactive than carbon.) Reject any answer that names more than one metal. | 1 |
| 10(d) | • oxygen • the volume of gas decreased by 21 cm3 (from 100 cm3 to 79 cm3), that is 21 %, which is the same as the proportion of oxygen in air (about one fifth) • Reject: air; nitrogen; carbon dioxide; water (water is a liquid, not a gas in the air); an answer that gives no data. The explanation mark needs a figure from the diagram. | 2 |
| 10(e) | calcium hydroxide and hydrogen (both needed; either order; accept Ca(OH)2 and H2; accept "limewater / calcium hydroxide solution"). Reject: calcium oxide; oxygen; hydroxide ions only. | 1 |
| 10(f) | • 1 mark: Ca2+ correct (in square brackets, charge 2+; no outer electrons or eight shown) • 1 mark: both F− correct (each in square brackets, charge −, eight outer electrons: seven of fluorine's own plus one from calcium shown by a different symbol) • Maximum 1 mark if either fluoride is wrong or a charge is missing. Accept all electrons shown as dots or all as crosses if the transfer is clear. Do not credit a shared pair (covalent bonding). Accept the fluoride ions drawn either side of Ca. | 2 |
| 10(g) | the statement “iron gains oxygen” must appear (to form iron(III) oxide). Extra correct statements about electrons (e.g. iron loses electrons) are accepted. Accept: iron combines with / reacts with oxygen; oxygen is added to iron. Reject: an answer in terms of electrons only, with no mention of iron gaining oxygen; iron loses oxygen; oxygen is oxidised. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 11(a) | • chlorine = 1 (the reaction is the most vigorous) • iodine = 3 (strong heating needed, least vigorous) and bromine = 2. Complete sequence 1, 2, 3 for chlorine, bromine, iodine = 2 marks • If chlorine = 1 is given but iodine / bromine are wrong or missing, award 1 mark. Reject the reverse order (3, 2, 1). | 2 |
| 11(b) | any value from −40 to 20 (°C) inclusive (real value −7 °C). Accept with or without the unit. Reject: 50 °C (or any value above 20); any value below −40. | 1 |
| 11(c) | gas because the boiling point (−34 °C) is below 25 °C / room temperature is above its boiling point. Both the state and the reason are needed. Reject: liquid; solid; "gas" with no reason or a reason based on the melting point only. | 1 |
| 11(d) | • sodium atoms have one outer shell electron (few outer electrons) and lose it (easily) to form a positive ion, so sodium is a metal • chlorine atoms have seven outer shell electrons (many outer electrons) and gain one electron to form a negative ion, so chlorine is a non-metal • Each mark needs the number of outer electrons (or few / many) linked to losing or gaining electrons. Accept "metals lose electrons and non-metals gain electrons". Reject: sodium has fewer shells; answers about melting point or conductivity only. | 2 |
| 11(e) | fluorine 2 and chlorine 3 (both needed). Reject: 7 or 17 (outer electrons / proton number); 2 and 8. | 1 |
| 11(f) | • three shared pairs of electrons (each one dot and one cross) between the nitrogen atom and the three hydrogen atoms • nitrogen has one non-bonding pair (lone pair), so eight electrons in its outer shell including the shared pairs; each hydrogen has two electrons • Accept without outer circles drawn; accept all electrons as dots or all as crosses if the three shared pairs and the lone pair are clear. Do not credit ions, double bonds, or a lone pair missing from nitrogen. | 2 |
| 11(g) | bromine is reduced (ticked) and the reason: bromine atoms gain electrons (to form bromide ions) / the oxidation state of bromine decreases from 0 to −1. The tick and a correct reason are both needed. Reject: oxidised; neither; reduced because it gains hydrogen or loses oxygen; a correct tick with a reason about sodium only. | 1 |