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) | • P: tin [1] • Q: impure [1] • R: zinc [1] • P and R melt and boil at the single temperatures of tin and of zinc. Q melts over a range of temperatures that is lower than 327 °C and boils over a range of temperatures that is higher than 1749 °C, so it is not pure lead. Accept the chemical symbols Sn and Zn. Reject: “pure” for Q; lead for P; tin for R. | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 2(a) | C (30 protons, 28 electrons: charge 2+) E is also a positive ion but has 48 electrons. Reject: E; F. | 1 |
| 2(b) | D (53 protons, 54 electrons: charge 1−) Reject: F (a negative ion, but its charge is 2−: 34 protons, 36 electrons). | 1 |
| 2(c) | E (50 + 69 = 119) Reject: any other letter. | 1 |
| 2(d) | A and B (both needed; either order) Same number of protons (30) and different numbers of neutrons (35 and 34). C also has 30 protons but it is an ion, not an atom, and has the same number of neutrons as A. Reject: A and C; B and C. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 3(a) | A and D [1 each] Reject: B or C. If more than two letters are given, 1 mark for two correct letters only if no more than one wrong letter is added; otherwise 0 for that mark. | 2 |
| 3(b)(i) | metals have high melting points / silver has a high melting point Reject: “metals melt easily”; a statement about conducting electricity only. | 1 |
| 3(b)(ii) | an alloy is a mixture of a metal (aluminium) with other elements / the elements are not chemically combined (not a compound) Reject: “it is a pure metal”; “it is an element”; “it is a compound of metals”. | 1 |
| 3(c) | • in the solid the ions are held in fixed positions (in the lattice) so they cannot move [1] • when molten the ions are free to move (and carry the charge) [1] • Reject: “electrons move”; “the molecules are free to move”; “it has no ions in the solid”. | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 4(a)(i) | aluminium oxide Accept: Al2O3. Reject: calcium oxide (basic). | 1 |
| 4(a)(ii) | carbon monoxide Accept: CO. Reject: nitrogen dioxide and sulfur dioxide (acidic). | 1 |
| 4(a)(iii) | calcium oxide Accept: CaO. Reject: aluminium oxide (it reacts with both). | 1 |
| 4(b)(i) | H+(aq) + OH−(aq) → H2O(l) Accept without state symbols. Reject: a full equation with calcium hydroxide and a named acid (this is not an ionic equation). | 1 |
| 4(b)(ii) | the hydroxide ions (from the alkali) react with / remove the hydrogen ions (so the concentration of hydrogen ions falls and the pH rises towards 7) Reject: “the alkali has a high pH” with no idea of ions reacting; “the acid is destroyed”. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 5(a) | 63 s (experiment 2 at 40 °C) Accept: 40 °C and 63 s. Reject: 41 s (it fits the pattern: the time roughly halves for each 10 °C rise); 40 °C alone. | 1 |
| 5(b) | repeat the experiment (at 40 °C / at each temperature) again / more times and calculate a mean (ignoring the anomalous result) Reject: changes that do not give repeats, such as using a bigger syringe, a different acid or more temperatures. | 1 |
| 5(c) | • at 50 °C the particles have more (kinetic) energy / move faster [1] • so they collide more frequently (more collisions per unit time) [1] • Reject: “more particles”; “the particles collide harder” with no idea of collision frequency. | 2 |
| 5(d) | exothermic (accept: an exothermic reaction) Reject: endothermic; “combustion” alone. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 6(a) | 80 − 20 = 60 ppb Accept 58 to 62. Reject: 80 or 20 on their own. | 1 |
| 6(b) | there are more vehicles / engines in use on a weekday (rush hour), so more nitrogen and oxygen react at the high temperature in the engines Accept: more vehicles, so more nitrogen dioxide formed. Reject: “there is more pollution” with no reference to vehicles or engines; the weather. | 1 |
| 6(c) | it dissolves in rain to form acid rain, which damages buildings / harms plants and lakes / kills fish Accept: breathing problems for people. Reject: global warming; damage to the ozone layer. | 1 |
| 6(d) | fractional distillation Reject: distillation alone; cracking; filtration. | 1 |
| 6(e) | the sugar cane takes in (absorbs) carbon dioxide by photosynthesis as it grows, which cancels out / offsets the carbon dioxide released when the bioethanol burns Reject: “bioethanol does not release carbon dioxide”; “bioethanol is cleaner”. | 1 |
| Part | Answer and mark points | Marks | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 7(a) |
| 7 | ||||||||||||||
| 7(b) | • correct formulae of the ions and the product: Cu2+, OH− and Cu(OH)2 [1] • balanced [1] • correct state symbols [1] • Cu2+(aq) + 2OH−(aq) → Cu(OH)2(s) • Missing or incorrect state symbols lose the third mark only. A full (non-ionic) equation, CuSO4(aq) + 2NaOH(aq) → Cu(OH)2(s) + Na2SO4(aq), earns 2 of the 3 marks if correct and balanced, because the question asks for an ionic equation. | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 8(a) | (2 × 1) + 16 = 18 | 1 |
| 8(b) | 1 volume of CH4 reacts with 2 volumes of O2: 50 × 2 = 100 cm3 | 1 |
| 8(c) | 1 volume of CH4 forms 1 volume of CO2: 50 cm3 | 1 |
| 8(d) | 100 ÷ 0.21 [1] = 476 cm3 [1] (ecf from (b)); accept 475 to 480 Reject: 100 × 0.21 = 21. | 2 |
| 8(e) | 50 cm3 = 0.050 dm3; 0.050 ÷ 24 = 0.00208 mol of CH4; × 2 = 0.00417 mol of H2O [1]; 0.00417 × 18 = 0.0750 g [1] (ecf from (a)); accept 0.075 or 0.0750 (0.08 to 1 s.f.) | 2 |
| Part | Answer and mark points | Marks | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 9(a) |
| 5 | |||||||||||||||
| 9(b) | • ethane is saturated / has no C=C double bond (only single bonds) [1] • addition polymerisation needs a C=C double bond to open up / so that the molecules can join together [1] • Reject: “ethane is an alkane” alone; “ethane is a gas”; “it has fewer hydrogen atoms”. | 2 | |||||||||||||||
| 9(c) | orange / brown (red-brown, yellow-brown) to colourless Reject: “clear” as the only colour; “the bromine disappears” with no colours. | 1 | |||||||||||||||
| 9(d) | it breaks large hydrocarbon molecules into smaller, more useful ones (alkenes, petrol) / it matches the demand for fractions with small molecules, which is greater than the supply from fractional distillation Reject: “to separate the fractions”; “to make crude oil purer”. | 1 | |||||||||||||||
| 9(e) | addition Reject: polymerisation; substitution; cracking. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 10(a) | • all four rows correct: Aisha not correct, Ben not correct, Chen correct, Dee not correct = 2 marks • two or three rows correct = 1 mark • Reject a row with two ticks or with no tick. | 2 |
| 10(b) | the elements are arranged in order of increasing proton number (accept: atomic number). Reject: "nucleon number" in any form; "number of neutrons"; "relative atomic mass"; "increasing number of electrons" with no mention of proton number. | 1 |
| 10(c) | the atoms (of elements in the same period) have the same number of (three) electron shells / three occupied shells (not three outer electrons). Accept: the electronic configurations all have three numbers. Reject: "the same number of electrons"; "the same number of outer electrons"; a statement that only repeats the table. | 1 |
| 10(d) | argon atoms have a full outer shell / eight electrons in the outer shell (electronic configuration 2.8.8). Accept: a stable / noble gas electronic configuration. Reject: "argon has no electrons"; "two electrons"; "argon is a gas"; "argon is stable" with no reference to the outer shell. | 1 |
| 10(e)(i) | 2.8.5 (accept 2,8,5 or a correct diagram of electron shells). Reject: 2.8.7; 2.8.8; 2.5; 15. | 1 |
| 10(e)(ii) | aluminium (accept Al). (The atom has 13 electrons, so proton number 13.) Reject: boron; gallium; any element outside Period 3. | 1 |
| 10(f) | • two sodium ions, each [Na]+ 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 sodium) • 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 sodium ions. Do not credit: a shared pair (covalent); one sodium ion only; a missing or wrong charge (the mark for that ion is lost). | 2 |
| 10(g) | sodium is oxidised (because it loses electrons). Accept: loss of electrons is oxidation; the oxidation state of sodium increases from 0 to +1. Reject: "sodium is reduced" with any reason; sulfur is oxidised; "gains oxygen" on its own. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 11(a) | • all four letters correct: W (below calcium), then X, then Z, then Y (above silver) = 2 marks. Fig. 11.1 completed: • two letters correct (e.g. one swap) = 1 mark • Reject a box with more than one letter. The order W, X, Z, Y comes from the acid results: very rapid, steady, slow, none. | 2 |
| 11(b) | • X is zinc, Y is copper and Z is iron (all three needed). Accept the symbols Zn, Cu, Fe. (Zinc is more reactive than iron, which is more reactive than copper; this matches the order of X, Z, Y in Fig. 11.1.) | 1 |
| 11(c) | W is more reactive than carbon (so carbon cannot remove the oxygen from the oxide of W / W is above carbon in the reactivity series). Accept: carbon is less reactive than W. Reject: "no reaction" with no comparison; "W is unreactive"; "W is too reactive" with no mention of carbon. | 1 |
| 11(d) | an arrowhead at the bottom end of the line, pointing down towards silver (the less reactive the metal, the easier it is to obtain from its ore; Table 11.1: the oxide of Y is reduced by gentle heating but the oxide of W is not reduced at all). Reject: an arrowhead at the top; arrowheads at both ends. | 1 |
| 11(e)(i) | D (between Z and Y). Reject: any other letter; two letters. | 1 |
| 11(e)(ii) | V reacts with the acid but Y does not (so V is more reactive than Y) and the oxide of V is reduced more easily (more gently) than that of Z (so V is less reactive than Z) [both comparisons needed for the mark]. Reject: a reason about one neighbour only; "V is in the middle". | 1 |
| 11(f)(i) | C (three shared pairs, a triple bond, and one lone pair on each nitrogen atom, so eight electrons around each atom and ten in total). Reject: any other letter. | 1 |
| 11(f)(ii) | each nitrogen atom has no lone pair / only six electrons around it, not eight / diagram B shows only 6 electrons but two nitrogen atoms have 10 outer electrons in total (5 each). Accept: the lone pairs are missing. Reject: "it has a triple bond"; "it has too many bonds". | 1 |
| 11(g) | copper(II) ions gain electrons (two electrons each, to form copper atoms). Accept: the oxidation state of copper decreases from +2 to 0. Reject: "gains electrons" with no species named; copper loses electrons; "loses oxygen" on its own. | 1 |