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) | fractional distillation Reject: simple distillation (it cannot separate liquids with close boiling points cleanly). | 1 |
| 1(b) | paper chromatography | 1 |
| 1(c) | measuring the melting point A pure solid melts at one sharp, fixed temperature; an impure solid melts over a range, at a lower temperature. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 2(a) | number of neutrons in W = 12 [1]; number of electrons in Y = 10 [1] W: 23 − 11 = 12. Y: 12 protons, charge 2+, so 12 − 2 = 10 electrons. | 2 |
| 2(b) | • same number of protons / same proton number (atoms of the same element) • different numbers of neutrons / different nucleon numbers Reject: “elements with different numbers of neutrons” (the particles are atoms of one element). | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 3(a) | M, because it conducts electricity when solid (accept: because it conducts when solid and when molten) Reject: “high melting point” alone (K also has a high melting point); the letter without a reason. | 1 |
| 3(b) | • in the solid, the ions are held in fixed positions (in a lattice) and cannot move / are not free to move • when molten, the ions are free to move (and carry the charge) Reject: electrons carry the charge in an ionic compound; “molecules”; “atoms”. | 2 |
| 3(c) | • weak forces of attraction between the molecules (weak intermolecular forces) • little energy is needed to overcome these forces / the (covalent) bonds within the molecules do not break Reject: covalent bonds are weak / covalent bonds break when L melts. | 2 |
| 3(d) | a mixture of a metal with (one or more) other element(s) (the other element may be a metal or a non-metal) | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 4(a) | hydrogen ion (H+) Accept: H+. Reject: hydroxide ion; “hydrogen” without H+ or “ion”. | 1 |
| 4(b) | calcium hydroxide is a base / alkali, which neutralises the acid (H+ ions) in the soil / removes H+ ions Both the idea of a base reacting and the acid being removed are needed for the mark. | 1 |
| 4(c) | H+(aq) + OH−(aq) → H2O(l) Accept: Ca(OH)2(s) + 2H+(aq) → Ca2+(aq) + 2H2O(l). State symbols must all be correct. Do not accept a non-ionic equation. | 1 |
| 4(d) | • ammonia (gas) is formed (ammonium ions react with the base, calcium hydroxide) • ammonia escapes / nitrogen is lost from the soil (not available to the plants) Accept: ammonium ions react with hydroxide ions to form ammonia and water. | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 5(a) | 20 s (accept 19–21) | 1 |
| 5(b) | • the particles move faster / have more (kinetic) energy at the higher temperature • so they collide more frequently (higher collision frequency) • Accept as an extra: more successful collisions per second. • Both ideas are needed for 2 marks. The direction (“more” / “higher”) must be stated. Reject: “more particles”, “more collisions” without “frequent”. | 2 |
| 5(c) | same amount (mass) of magnesium / magnesium is the limiting reactant [1] Accept: acid in excess so all the magnesium reacts. Reject: temperature does not affect the final volume. | 1 |
| 5(d) | heat energy is given out to the surroundings / exothermic | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 6(a) | incomplete combustion / there is not enough (a limited supply of) oxygen Accept: not enough air. Reject: “no oxygen”. | 1 |
| 6(b) | it is toxic / poisonous (accept: causes headaches, dizziness, unconsciousness or death; reduces the oxygen carried by the blood) Reject: causes acid rain / global warming. | 1 |
| 6(c) | respiration (by living things) / decay (decomposition) of dead plants and animals / volcanic eruptions Reject: burning of petrol, coal, wood or other fuels (stated in the question); photosynthesis; factories (with no process named). | 1 |
| 6(d) | the sugar cane can be regrown (replaced) as quickly as the fuel is used / new crops can be grown each year Reject: “it will never run out” with no reference to growing plants. | 1 |
| 6(e) | the sugar cane absorbs (takes in) carbon dioxide by photosynthesis as it grows, which offsets / cancels out the carbon dioxide released when bioethanol burns (petrol releases carbon dioxide that was stored underground with no offset) | 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. A wrong formula loses the formulae mark; the balancing mark may still be awarded if the equation as written is balanced. Ionic equations with state symbols are also accepted. • FeCO3(s) + H2SO4(aq) → FeSO4(aq) + CO2(g) + H2O(l) • or FeSO4(aq) + 2NaOH(aq) → Fe(OH)2(s) + Na2SO4(aq) (ionic: Fe2+(aq) + 2OH−(aq) → Fe(OH)2(s)) • or FeSO4(aq) + 2NH3(aq) + 2H2O(l) → Fe(OH)2(s) + (NH4)2SO4(aq) • or FeSO4(aq) + Ba(NO3)2(aq) → BaSO4(s) + Fe(NO3)2(aq) (ionic: Ba2+(aq) + SO42−(aq) → BaSO4(s)) • or CO2(g) + Ca(OH)2(aq) → CaCO3(s) + H2O(l) (accept: the test for U is shown in the chart) | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 8(a) | • average mass of an atom of the element • compared with one-twelfth of the mass of an atom of carbon-12 | 2 |
| 8(b) | 7 + 16 + 1 = 24 | 1 |
| 8(c) | 240 ÷ 24 = 10.0 mol (ecf from (b)) | 1 |
| 8(d) | 2 mol LiOH react with 1 mol CO2: 10.0 ÷ 2 = 5.0 mol [1]; 5.0 × 24 = 120 dm3 [1] (ecf from (c)) | 2 |
| 8(e) | 200 cm3 = 0.200 dm3; 0.20 ÷ 0.200 = 1.0 mol / dm3 | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 9(a) | propene: C3H6 [1]; six carbon atoms: C6H12 [1] | 2 |
| 9(b) | CnH2n | 1 |
| 9(c) | similar chemical properties / a gradual change (gradation) in physical properties (e.g. melting point, boiling point) / the same functional group (C=C) / consecutive members differ by CH2 Reject: same physical properties; same molecular formula. | 1 |
| 9(d) | C=C double bond between two carbon atoms; CH3 group (three C–H bonds) on the third carbon; each carbon has four bonds in total. | 1 |
| 9(e) | • propene: orange / brown bromine water turns colourless [1]; propane: bromine water stays orange / brown [1] • The reagent (aqueous bromine) is given in the question, so both results are needed for 2 marks; one result gets 1. Reject: “clear” on its own; limewater; burning splint. | 2 |
| 9(f) | repeat unit –CH2–CH(CH3)– shown twice, with CH3 on alternate carbons of the C–C chain [1]; continuation bonds at both ends and no C=C [1]. Accept CH3 drawn above or below. Reject: CH3 on adjacent carbons; a single repeat unit in brackets with n; C=C in the chain. | 2 |
| 9(g) | C3H6 + H2 → C3H8 Accept displayed or structural formulae, e.g. CH3CH=CH2 + H2 → CH3CH2CH3; state symbols not required. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 10(a) | • Y first (most reactive) and X last (least reactive) • W before Z (W is more reactive than Z). Correct order Y, W, Z, X = 2 marks | 2 |
| 10(b) | magnesium (accept Mg). (Order of reactivity is Ca, Mg, Zn, Cu, so Y = calcium, W = magnesium, Z = zinc, X = copper.) | 1 |
| 10(c)(i) | • oxygen (accept air) and water, both needed for the mark. Reject: carbon dioxide; salt; water alone; air alone. | 1 |
| 10(c)(ii) | • E (oxygen from the air and water are present, with sodium chloride to speed up rusting). Note: A has no water; B and D have no oxygen (boiled water, oil layer); C has oxygen and water but no sodium chloride, so it rusts more slowly than E. Reject C. | 1 |
| 10(d) | the paint forms a barrier / coats the iron so that oxygen (air) and water cannot reach the iron. Accept: keeps oxygen and water away from the iron. Reject: stops air only; stops water only; paint is more reactive than iron. | 1 |
| 10(e) | calcium is more reactive than carbon, so carbon cannot remove the oxygen from calcium compounds (copper is less reactive than carbon, so carbon can). Accept: calcium is more reactive than copper / higher in the reactivity series; its compounds / oxide are more stable; it holds on to oxygen more strongly. Reject: calcium is harder / more difficult to extract (restates the question); calcium reacts with water (alone). | 1 |
| 10(f) | • [Mg]2+ in square brackets with charge 2+ and either no electrons or eight electrons (crosses) shown in the outer shell • [O]2− in square brackets with charge 2− and eight outer electrons: six dots (O) and two crosses (Mg), dots and crosses different symbols • Accept electrons shown all as dots or all as crosses if consistent and the transfer is clear. Do not credit a shared pair (covalent). A missing charge loses that ion's mark. | 2 |
| 10(g) | magnesium atoms lose electrons (to form Mg2+ ions). Accept: electrons are transferred from Mg to O; the oxidation state of Mg increases from 0 to +2. Reject: "gains oxygen" on its own; "loses electrons" without reference to magnesium. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 11(a) | • chlorine is the most reactive / Cl first (chlorine displaces both bromide and iodide ions) • bromine is more reactive than iodine / Br before I (bromine displaces iodide but not chloride ions). Correct order chlorine, bromine, iodine = 2 marks | 2 |
| 11(b) | potassium chloride and bromine (both required, either order). Accept the formulae KCl and Br2. (Cl2 + 2KBr → 2KCl + Br2) | 1 |
| 11(c) | • fluorine has the electronic configuration 2.7 and chlorine has 2.8.7 (accept 2,7 and 2,8,7) • both have seven electrons in the outer shell / both have the same number of outer shell electrons | 2 |
| 11(d) | bromine. Accept: Br2. Reject: bromide; potassium bromide; chlorine. | 1 |
| 11(e) | no reaction, because iodine is less reactive than chlorine (than bromine) / iodine cannot displace chlorine. Accept the evidence: bromine does not react with potassium chloride (experiment 3) and iodine does not react with potassium bromide (experiment 5); or chlorine displaces iodine (experiment 2), so iodine is less reactive. Both the prediction and the reason are needed. Reject: iodine is a solid. | 1 |
| 11(f) | • one shared pair of electrons (one dot and one cross) in the overlap between the hydrogen atom and the chlorine atom • chlorine has three non-bonding pairs of electrons (lone pairs), so eight electrons in its outer shell including the shared pair; hydrogen has no other electrons • Accept without outer circles drawn; Cl may be shown with only its outer shell. Do not credit: ions drawn (H+ and Cl−); a double bond; extra electrons on hydrogen. | 2 |
| 11(g) | chlorine, because it oxidises bromide ions (to bromine) / it gains electrons (is reduced) / its oxidation state decreases from 0 to −1. Both the species and the reason are needed. Accept: Cl2. Reject: potassium bromide / bromide ions; chlorine “loses electrons”. | 1 |