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) | B, then C, then A (filter; wash; dry) [1] — all three in the correct order Reject: any order with step A (drying) before step C (washing). | 1 |
| 1(b) | filtration (accept: filtering) Reject: evaporation; crystallisation; distillation; chromatography. | 1 |
| 1(c) | to remove the soluble substance (sodium chloride solution) left on the solid / to remove soluble impurities / so the barium sulfate is pure Reject: “to clean it” with no impurity named; “to dissolve the barium sulfate”; “to cool it”. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 2(a) | 2,5 (accept 2.5 or a correct shell diagram) J has proton number 7, so 7 electrons: 2 in the first shell and 5 in the second. Reject 2,8,5; 5,2. | 1 |
| 2(b) | L L (proton number 10) has the configuration 2,8: a full outer shell, in the Group 18 column of Fig. 2.1. | 1 |
| 2(c) | M M has 14 electrons: 2,8,4. K also has three shells but only two outer electrons (2,8,2). Reject K. | 1 |
| 2(d) | the total number of protons and neutrons (nucleons) in the nucleus of an atom (accept: in one atom) Reject: the number of protons (that is the proton number); the number of protons and electrons; “the mass number” alone. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 3(a) | • the fluorine atom gains one electron (to form F−) • so that it has a full outer shell / the electronic configuration of a noble gas (2,8) • Reject: the atom loses an electron; the atom gains a proton or shares an electron. Accept: 2,7 changes to 2,8. | 2 |
| 3(b) | solid: no; molten: yes; dissolved in water: yes [1 for all three correct] | 1 |
| 3(c) | • in the solid the ions are held in fixed positions in the lattice, so they cannot move • when molten or dissolved the ions are free to move (and carry the charge) • Reject: electrons carry the charge; “molecules”; “atoms”; “the solid has no ions”. | 2 |
| 3(d) | the copper and zinc are not chemically combined / no chemical reaction between them / the proportions of copper and zinc can vary / each metal keeps its own properties Reject: “it contains two elements” alone (a compound also contains two elements); “it is stronger than copper”. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 4(a) | tomato juice: orange (accept orange-red or orange-yellow) [1]; liquid hand soap: blue (accept blue-violet) [1] Reject: red or yellow for pH 4; green or plain violet for pH 9. | 2 |
| 4(b) | magnesium chloride [1]; water [1] (either order) Accept formulae: MgCl2, H2O. Reject: magnesium chlorine; hydrogen; magnesium oxide. | 2 |
| 4(c) | the mixture is neutral (pH 7) / all the acid has been neutralised (reacted) Reject: the mixture is alkaline; the mixture is a base. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 5(a) | All four points correctly plotted (to within half a small square) and one smooth curve through them (not straight lines joining the points); the curve falls and levels off. Both parts are needed for the mark. | 1 |
| 5(b) | 23 to 25 s read from the candidate’s curve at 0.25 mol / dm3 (24 s; concentration × time = 6.0, so 6.0 ÷ 0.25 = 24 s) Accept a value read correctly from the candidate’s own curve if the curve is a fair line through the points. | 1 |
| 5(c) | • experiment 1 has a higher concentration / more particles (of sodium thiosulfate) per unit volume • so the particles collide more frequently (higher collision frequency) • Reject: “more particles” with no “per unit volume”; “more collisions” with no “frequent” / “per second”; “particles move faster”; “more energy”. | 2 |
| 5(d) | endothermic (the temperature falls because energy / heat is taken in from the surroundings) Reject: exothermic. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 6(a) | volcanoes / volcanic eruptions Reject: lightning (a source of nitrogen oxides); burning fossil fuels or petrol (not natural); car exhausts. | 1 |
| 6(b) | the acid in acid rain reacts with calcium carbonate (the carbonate in the limestone), which dissolves / wears away Accept: limestone is a carbonate and carbonates react with acid to give carbon dioxide. Reject: “acid rain burns the statue”; “the acid rain is hot”; the acid reacts with the metal. | 1 |
| 6(c) | breathing (respiratory) problems / irritates the lungs or throat / makes asthma worse Reject: it is toxic (not specific enough); it causes cancer; it causes global warming. | 1 |
| 6(d) | carbon dioxide (accept CO2) Reject: water; oxygen; carbon monoxide. | 1 |
| 6(e) | the carbon dioxide released is (almost) offset by the carbon dioxide taken in by the growing plants, so the net increase is only about 2 tonnes (burning coal releases carbon dioxide with no offset) Accept: the amounts are similar, so little extra carbon dioxide is added. Reject: “bioethanol does not produce carbon dioxide”. | 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. • 2Zn(s) + O2(g) → 2ZnO(s) • or ZnO(s) + 2HNO3(aq) → Zn(NO3)2(aq) + H2O(l) • or Zn(NO3)2(aq) + 2NaOH(aq) → Zn(OH)2(s) + 2NaNO3(aq) (ionic: Zn2+(aq) + 2OH−(aq) → Zn(OH)2(s)) • or Zn(NO3)2(aq) + 2NH3(aq) + 2H2O(l) → Zn(OH)2(s) + 2NH4NO3(aq) • or the ionic equation ZnO(s) + 2H+(aq) → Zn2+(aq) + H2O(l) (accepted) • The reaction in which the precipitate dissolves in excess alkali is not required (the product is not on the syllabus); no mark for it. | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 8(a) | 21.30, 20.10, 19.90, 20.00 (all four correct) [1] Final reading − initial reading in each titration. | 1 |
| 8(b) | (20.10 + 19.90 + 20.00) ÷ 3 = 20.00 cm3 (accept 20.0) All three used results agree within 0.20 cm3 (the largest difference is exactly 0.20 cm3). The rough titration (21.30 cm3) is not used; it does not agree with the others. Reject 20.33 (the mean of all four results). | 1 |
| 8(c) | 0.100 × 20.00 ÷ 1000 = 2.00 × 10−3 mol (0.00200) (ecf from (b)) | 1 |
| 8(d) | 1 mol NaOH reacts with 1 mol HCl, so 2.00 × 10−3 mol (ecf from (c)) | 1 |
| 8(e) | 25.0 cm3 = 0.0250 dm3; 2.00 × 10−3 ÷ 0.0250 = 0.0800 mol / dm3 (ecf from (d)) | 1 |
| 8(f) | 23 + 16 + 1 = 40 | 1 |
| 8(g) | 0.0800 × 40 = 3.20 g / dm3 (accept 3.2) (ecf from (e) and (f)) | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 9(a) | 30 to 150 °C (accept: from 30 °C to 150 °C; this is the petrol fraction) Reject: a single temperature; the range of another fraction. | 1 |
| 9(b) | fractional distillation Reject: distillation; simple distillation; evaporation; cracking. | 1 |
| 9(c) | the boiling range increases (gets higher) as the number of carbon atoms increases / as the molecules get larger Reject: decreases; a statement about one fraction only. | 1 |
| 9(d) | a compound that contains carbon and hydrogen only Reject: “a mixture of carbon and hydrogen”; “contains carbon and hydrogen” with no “only”. | 1 |
| 9(e) | CnH2n+2 | 1 |
| 9(f) | Two carbon atoms joined by a single bond; each carbon atom has four single bonds; every C–H bond drawn (six H atoms in total). Reject: CH3CH3 (not displayed); a carbon atom with more or fewer than four bonds. | 1 |
| 9(g) | C3H8 + 5O2 → 3CO2 + 4H2O Accept displayed or structural formulae; state symbols not required. Reject: carbon monoxide as a product; an unbalanced equation. | 1 |
| 9(h) | • K [1] • butene is unsaturated / has a C=C double bond, which reacts with (adds) bromine, so the orange colour disappears; butane is saturated (single bonds only) and does not react [1] • The second mark needs the idea of a double bond / unsaturation. Reject: the letter with no reason; “butane is a gas”. | 2 |
| 9(i) | cracking breaks large (hydrocarbon) molecules into smaller, more useful molecules (such as petrol) to match the demand for them / it also makes alkenes (and hydrogen) that are needed to make plastics Reject: “it separates the fractions”; “it makes crude oil”. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 10(a) | • all three correct: chlorine Q (gas: molecules far apart and moving randomly), bromine R (liquid: molecules close together but irregular), iodine P (solid: molecules in a regular arrangement) = 2 marks • one halogen correct (the other two swapped) = 1 mark. Accept the answer given as a table or in a sentence. | 2 |
| 10(b) | chlorine is more reactive than bromine (reactivity decreases down the group / chlorine is above bromine in Group 17). Accept: chlorine is a stronger oxidising agent than bromine. Reject: chlorine is a gas / smaller / has a lower relative atomic mass; a reason about the colour only; "chlorine is reactive" with no comparison with bromine. | 1 |
| 10(c) | seven (7) and a reason: bromine is in Group 17 / elements in the same group have the same number of outer shell electrons as each other (as chlorine, which has the configuration 2.8.7). Both the number and the reason are needed. Reject: 17; eight; "because it is a halogen" with no reference to the group or to outer electrons. | 1 |
| 10(d) | • X is sodium bromide and Y is sodium iodide (both needed). Accept the formulae NaBr and NaI. (Chlorine displaces bromine from X, giving orange, but iodine cannot. Bromine and chlorine both displace iodine from Y, giving brown.) Reject: potassium halides; bromide and iodide with no sodium. | 1 |
| 10(e) | • no reaction / no change (bromine does not displace chlorine) • bromine is less reactive than chlorine / chlorine is above bromine in Group 17 (so bromine cannot displace chlorine; accept use of Table 10.1 or of the trend that reactivity decreases down the group). Reject: a reason with no comparison; "bromine is a liquid"; any prediction that a reaction occurs (the reason mark is then not awarded). | 2 |
| 10(f) | • four shared pairs of electrons: one between the carbon atom and each of the four chlorine atoms (each pair shown as one dot and one cross) • each chlorine atom has three non-bonding pairs (lone pairs), so eight electrons in its outer shell including the shared pair; carbon has eight electrons in its outer shell and no lone pairs • Accept all electrons as dots or as crosses if the shared pairs are clear; accept without outer circles; accept the four chlorine atoms in any arrangement around carbon. Do not credit: ions drawn; a double bond; fewer or more than four bonds; chlorine atoms with unpaired electrons. | 2 |
| 10(g) | the oxidation state of iodine increases from −1 to 0 (both values needed). Accept: iodide ions lose electrons (to form iodine). Reject: iodine gains electrons; a change from 0 to −1; "increases" with no values; bromine is oxidised. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 11(a) | • all three correct: Q is potassium (steepest curve: the reaction finishes first, so the most reactive), P is sodium, R is lithium (least steep curve: slowest, the least reactive) = 2 marks • one metal correct (the other two swapped) = 1 mark. Accept symbols K, Na, Li. Reactivity increases down Group 1: Li, Na, K. | 2 |
| 11(b) | violet (accept: purple; blue-purple). The solution is strongly alkaline. Reject: green; yellow; orange; red. | 1 |
| 11(c) | both have one electron in the outer shell (accept: lithium 2.1 and potassium 2.8.8.1 both end in 1; they are in the same group, so have the same number of outer shell electrons). Reject: both have the same number of shells; both have the same number of electrons; "both are metals". | 1 |
| 11(d) | increases (down the group): the order from the graph is lithium, sodium, potassium. Accept: more reactive / more rapid reaction with water further down. Reject: decreases; "gets faster" with no link to the group. | 1 |
| 11(e) | • the curve for Z starts at the origin and is steeper than the curve for Q (potassium), so it levels off at an earlier time than Q (reactivity increases down Group 1) • the curve for Z levels off at 24 cm3 and is labelled Z. Reject: a curve that levels off above or below 24 cm3; a curve less steep than Q; a curve that crosses another curve. | 2 |
| 11(f) | • two potassium ions, each [K]+ in square brackets with the charge + and either no outer electrons or the eight electrons of its (new) outer shell shown • one sulfide ion, [S]2− in square brackets with the charge 2− and eight electrons in the outer shell: six of one symbol (sulfur's own) and two of the other (one from each potassium) • Accept all electrons as dots or crosses if the transfer is clear; accept ions with outer circles; accept the sulfide ion between or beside the potassium ions. Do not credit: a shared pair (covalent); one potassium ion only; a missing or wrong charge (the mark for that ion is lost). | 2 |
| 11(g) | potassium: oxidised and hydrogen in water: reduced (both rows correct for the mark). (Potassium atoms lose electrons to form K+ ions: the oxidation state of potassium increases from 0 to +1. Hydrogen in water gains electrons to form H2: its oxidation state decreases from +1 to 0.) Reject: two ticks in one row; both substances oxidised; both reduced. | 1 |