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) | • step 1: not enough water (a few drops) to dissolve all the salt [1] – add enough (an excess of) water to dissolve all the salt (and stir) • step 2: no filter paper in the funnel (so the sand passes through) [1] – fit a (folded) filter paper in the funnel before pouring in the mixture • step 4: a measuring cylinder is not heated / is not made to be heated / will crack or fall over [1] – pour the liquid into an evaporating dish (accept: a beaker; an evaporating basin) and heat that • 1 mark for each correct row: the step number, the mistake and its correction are all needed (the step number may be missing if the mistake is clear). Any order. • Steps 3 and 5 are correct: no credit for either. Reject for step 1: “use hot water” or “stir for longer” alone. Reject for step 2: “use a bigger funnel”. Reject for step 4: “do not use a Bunsen burner” or “heat strongly” (the mistake is the container). | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 2(a) | • 5426Fe: 28 neutrons and 26 electrons [1] • 5626Fe3+: 26 protons and 23 electrons [1] • 3115P3−: 16 neutrons and 18 electrons [1] • 1 mark for each row; both blanks in the row must be correct. 54 − 26 = 28. Fe3+ has lost three electrons, so 26 − 3 = 23. 31 − 15 = 16; P3− has gained three electrons, so 15 + 3 = 18. | 3 |
| 2(b) | 5726Fe Nucleon number 57 (26 + 31) written above, proton number 26 written below, with the symbol Fe. Both numbers needed; accept the numbers to the left of Fe in the same positions. Reject: 31 or 5 as the nucleon number; the numbers swapped. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 3(a)(i) | C Each molecule of steam contains atoms of two different elements (oxygen and hydrogen) joined together. Reject: A, B, D, E. | 1 |
| 3(a)(ii) | D Two different kinds of molecule (nitrogen and oxygen) that are not joined to each other. Reject: B (one kind of molecule only). | 1 |
| 3(a)(iii) | A and B (both needed; either order) Each contains atoms of one kind only. Reject any answer that includes C, D or E. | 1 |
| 3(b) | The atoms are in regular layers / rows, with a few larger circles (tin atoms, shown dark) among the copper atoms. Do not award the mark if all the circles are the same size (that is a pure metal), if the layers are not regular, or if the atoms are drawn as molecules / joined pairs. An alloy is a mixture of a metal with another element. | 1 |
| 3(c) | • sodium chloride has a giant lattice of oppositely charged ions held together by strong forces of (electrostatic) attraction; much energy is needed to overcome them (so a high melting point) • oxygen consists of simple molecules with only weak forces of attraction between the molecules; little energy is needed to overcome them (so a low melting point) • Both substances must be compared for 2 marks. Reject: covalent bonds in oxygen break on melting; “sodium chloride has strong covalent bonds”; ideas about metallic bonding. | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 4(a) | • either method; any three marks from the points below (maximum 3) • both methods: the same volume of each liquid is put into separate (identical) test tubes / beakers (fair test) [1] • Universal Indicator: add the same number of drops of Universal Indicator (or dip Universal Indicator paper) in each liquid [1]; compare the colour with the pH colour chart / record the pH, and the liquid with the lower pH (colour nearer red) is more acidic [1] • magnesium: add the same length (mass) of magnesium ribbon to each liquid [1]; the liquid that gives more bubbles / bubbles faster (hydrogen) is more acidic [1] • Reject: “taste each liquid”; a conclusion with no observation or measurement; using different volumes of the two liquids (not a fair comparison) for the first mark. Accept pH paper or a pH meter for the indicator. | 3 |
| 4(b)(i) | neutralisation Reject: displacement; precipitation; redox. | 1 |
| 4(b)(ii) | 7 Accept: pH 7. Reject: a range (6–8); 0; 14. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 5(a) | curve X rises more steeply than the curve for experiment 1 (reaches the maximum volume at a shorter time) [1] curve X levels off at the same maximum volume, 120 cm3 (accept 115–125 cm3) [1] The curve must start at the origin. Reject: a curve that levels off at a different volume; a straight line; a curve that crosses the curve for experiment 1. The same amount of baking soda is used, so the same amount of gas forms: 0.42 ÷ 84 = 0.0050 mol, and 0.0050 × 24 000 = 120 cm3. | 2 |
| 5(b) | • the particles move faster / have more (kinetic) energy at the higher temperature • so the particles collide more frequently (accept: more successful / effective collisions per second) • Both marks need a reference to temperature leading to particle energy / speed, and to collisions. Reject: “more particles”; “the particles collide harder” with nothing else; “more collisions” with no reference to time or frequency. | 2 |
| 5(c) | endothermic and the temperature falls / the reaction takes in heat (energy) from the surroundings Reject: exothermic; a reason with no type of reaction. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 6(a) | there is not enough oxygen (a limited supply of air) so the methane burns incompletely (incomplete combustion) Reject: “the window is closed” (the yellow flame gives more carbon monoxide with the window open as well); “the gas burns faster”; “it is hotter”. | 1 |
| 6(b) | it is toxic / poisonous or it reduces the amount of oxygen the blood can carry (it combines with haemoglobin) Reject: “it is acidic”; “it causes acid rain”; “it damages the ozone layer”; “it is flammable”. | 1 |
| 6(c) | lightning (accept: lightning storms; thunderstorms) Reject: car engines; gas hobs; burning fossil fuels; volcanoes. | 1 |
| 6(d) | the carbon dioxide released when the fuel burns is (about) equal to the carbon dioxide taken in by the plants while they grew / no net increase in carbon dioxide in the air Reject: “it does not make carbon dioxide”; “it does not pollute”; “it is renewable” alone. | 1 |
| 6(e) | 191 − 180 = 11 kg Reject: 191 (nothing subtracted); −11. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 7(a) | oxygen relights a glowing splint = oxygen. Accept the formula. Reject any other entry of the list. | 1 |
| 7(b) | sulfur dioxide decolourises acidified potassium manganate(VII) = sulfur dioxide. Accept the formula. Reject any other entry of the list. | 1 |
| 7(c) | aluminium ion a zinc ion also gives a white precipitate that dissolves in excess aqueous sodium hydroxide, but its precipitate with aqueous ammonia dissolves in excess too. Accept the formula. Reject any other entry of the list. | 1 |
| 7(d) | calcium ion white precipitate insoluble in excess aqueous sodium hydroxide and no precipitate with aqueous ammonia. Accept the formula. Reject any other entry of the list. | 1 |
| 7(e) | copper(II) ion Data Sheet: copper(II) hydroxide is the only light blue hydroxide. Accept the formula. Reject any other entry of the list. | 1 |
| 7(f) | iron(III) ion Data Sheet: iron(III) hydroxide is red-brown (iron(II) hydroxide is green). Accept the formula. Reject any other entry of the list. | 1 |
| 7(g) | sulfate ion white precipitate with barium nitrate after nitric acid is the sulfate test. Accept the formula. Reject any other entry of the list. | 1 |
| 7(h) | • correct formulae of all reactants and products [1]; balanced (atoms and charges) [1]; correct state symbols [1] • Missing or incorrect state symbols: lose the third mark only. Correct formulae and state symbols but unbalanced: 2 marks (balancing mark lost). Balancing mark needs correct formulae. • Al3+(aq) + 3OH−(aq) → Al(OH)3(s) • or Ca2+(aq) + 2OH−(aq) → Ca(OH)2(s) • or Cu2+(aq) + 2OH−(aq) → Cu(OH)2(s) • or Fe3+(aq) + 3OH−(aq) → Fe(OH)3(s) • or Ba2+(aq) + SO42−(aq) → BaSO4(s) • Full (non-ionic) equations with state symbols, for example using sodium hydroxide or barium nitrate, are also accepted if balanced. | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 8(a) | the average mass of an atom of the element compared with / relative to 1⁄12 of the mass of an atom of carbon-12 Accept: “weighted average mass of the isotopes of an element, relative to 1/12 of the mass of one carbon-12 atom”. Reject: “the mass of an atom” with no comparison; the mass of one mole. | 1 |
| 8(b) | 23 + 35.5 = 58.5 | 1 |
| 8(c) | the graph levels off at 20.0 cm3 (accept 19.5–20.5), so 0.200 × 20.0 ÷ 1000 = 0.00400 mol (accept 0.0039–0.0041; ecf for another volume read from the graph) | 1 |
| 8(d) | 1 mol AgNO3 reacts with 1 mol NaCl, so 0.00400 mol NaCl [1]; 0.00400 × 58.5 = 0.234 g [1] (ecf from (b) and (c)) | 2 |
| 8(e)(i) | 0.234 ÷ 0.0250 = 9.36 g / dm3 (ecf from (d)); accept 9.4 | 1 |
| 8(e)(ii) | 0.00400 ÷ 0.0250 = 0.160 mol / dm3 (ecf from (c)); accept 9.36 ÷ 58.5 | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 9(a) | • ethene: C2H4 and alkene [1] • ethanol and alcohol [1] • ethanoic acid: carboxylic acid [1] • 1 mark for each row; both blanks in the row must be correct. Accept CH2=CH2 for the formula of ethene. Reject: alkane for ethene; “acid” or “organic acid” alone for ethanoic acid. | 3 |
| 9(b)(i) | methane Reject: ethene (general formula CnH2n). | 1 |
| 9(b)(ii) | ethene Reject: methane; ethanol; ethanoic acid (its double bond is C=O, not C=C). | 1 |
| 9(b)(iii) | ethanol Reject: ethanoic acid (made from ethanol). | 1 |
| 9(b)(iv) | ethanoic acid Reject: ethene; ethanol. | 1 |
| 9(c) | a family (group) of compounds with the same general formula / the same functional group and similar chemical properties Accept: “the formulae of successive members differ by CH2”; “gradual change in physical properties”, if the idea of a family of similar compounds is clear. Reject: “same molecular formula”; “compounds with the same atoms”. | 1 |
| 9(d) | aqueous bromine / bromine water Reject: limewater; Universal Indicator; acidified potassium manganate(VII). | 1 |
| 9(e) | addition (polymerisation) Reject: condensation; cracking; “polymerisation” alone. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 10(a) | • reactivity increases from lithium to potassium / down the group. Reject: decreases; "potassium is most reactive" with no trend • a supporting observation from the table, for example: the time taken to disappear decreases (about 5 minutes, 1 minute, a few seconds); the metal moves faster; sodium and potassium melt but lithium does not; only potassium burns with a flame. Reject: "bubbles" with no comparison; a statement not taken from the table | 2 |
| 10(b) | they float (on the water). Reject: "they move"; "they fizz"; "they melt" | 1 |
| 10(c) | hydrogen (accept H2). (2K + 2H2O → 2KOH + H2) Reject: oxygen; potassium hydroxide; steam | 1 |
| 10(d) | • method and identification (all three metals needed): add a (very) small piece of each metal in turn to (separate) cold water; the metal that burns with a lilac flame / reacts in a few seconds / moves most quickly is potassium; the metal that melts to a ball but has no flame is sodium; the metal that does not melt and moves slowly is lithium. Accept any correct, distinguishing observation for each metal. Reject: adding the three metals together; identification by colour or appearance before the test • any one safety precaution, for example: wear eye protection; use a safety screen; use a very small piece of metal; handle the metal with forceps (not fingers); stand back. Reject: "be careful"; "wear a lab coat" alone | 2 |
| 10(e) | 2.8.8.1 (accept 2,8,8,1 or a correct diagram of electron shells). Reject: 2.8.1; 2.8.9; 19 | 1 |
| 10(f) | • 1 mark: potassium ion correct: K+ in square brackets with the charge +, and either no electrons shown or eight electrons in its outer shell • 1 mark: chloride ion correct: Cl− in square brackets with the charge − and eight electrons in the outer shell (seven from chlorine shown as one kind of symbol and one from potassium shown as the other) • Accept: all electrons as dots or all as crosses if the transfer is clear; ion circles drawn or not. Do not credit: a shared pair of electrons (covalent bonding); a missing or wrong charge loses the mark for that ion. | 2 |
| 10(g) | electrons are transferred from potassium (atoms) to chlorine (atoms), so potassium is oxidised and chlorine is reduced at the same time (potassium loses electrons and chlorine gains electrons). Reject: a statement about only one of the two substances; "gain / loss of oxygen"; "chlorine and potassium react" | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 11(a) | • zinc: bubbles at a rate between those of magnesium and iron, for example a steady / moderate / fairly rapid stream of bubbles; the metal dissolves at a moderate rate. Reject: a "very rapid" or a "slow" stream (the same as magnesium or iron); "no bubbles"; "no reaction" • silver: no bubbles / no reaction / no change. Reject: "slow bubbling"; "it dissolves" | 2 |
| 11(b) | magnesium chloride (accept MgCl2). (Mg + 2HCl → MgCl2 + H2) Reject: magnesium chlorine; magnesium oxide; hydrogen chloride; chloride | 1 |
| 11(c) | oxygen (accept air). Reject: carbon dioxide; nitrogen; salt; acid; hydrogen | 1 |
| 11(d) | • the coating is a barrier that stops oxygen and / or water reaching the iron. Accept: keeps air or water away from the iron. Reject: "the plastic stops the iron reacting"; "plastic is less reactive than iron"; "waterproof" with no link to the iron • at the scratch the iron is in contact with oxygen (air) and water (both needed), so it rusts. Accept: the barrier is broken at the scratch. Reject: "the plastic reacts"; oxygen or water alone | 2 |
| 11(e) | silver, because it is the least reactive of the four metals / it does not react with the acid. Both the metal and a reason are needed. Reject: magnesium; "silver is rare"; a reason with the wrong metal | 1 |
| 11(f) | • four shared pairs of electrons, one between the carbon atom and each of the four hydrogen atoms (each overlap has one dot and one cross) • carbon has eight electrons in its outer shell and each hydrogen has two electrons; no lone pairs (non-bonding electrons) on carbon • Accept without outer circles drawn; accept all carbon electrons as dots and all hydrogen electrons as crosses (or the reverse). Do not credit: ions drawn; double bonds; extra electrons on carbon or hydrogen; fewer than four hydrogen atoms. | 2 |
| 11(g) | from 0 to +2 (both values needed; accept increases from 0 to +2). Reject: +2 to 0; 0 to −2; "increases" with no values | 1 |