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) | 27.0 (accept 27) Reject: 26 or 28. | 1 |
| 1(b) | 25.80 − 3.20 = 22.60 (accept 22.6; accept any value from 22.55 to 22.65) The readings are 3.20 cm3 before and 25.80 cm3 after. Reject: the sum of the readings, or a volume found by adding instead of subtracting. | 1 |
| 1(c) | burette Its scale has divisions of 0.1 cm3, so a volume can be read to 0.05 cm3; the measuring cylinder has divisions of 2 cm3. Reject: measuring cylinder. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 2(a) | X (5 protons) Reject: P (it has 6 protons and 5 neutrons). | 1 |
| 2(b) | P (6 protons + 5 neutrons = 11) Reject: X (nucleon number 10). | 1 |
| 2(c) | U (3 protons: the atom has 3 electrons, 2.1, so one outer shell electron) Reject: S (Group 2). | 1 |
| 2(d) | S (12 protons: the atom has 12 electrons, 2.8.2) Reject: P, X, U, Z (all have two electron shells). | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 3(a) | • all five rows correct [3]; four rows correct [2]; two or three rows correct [1] • aluminium: metallic; lithium chloride: ionic; dimethyl carbonate: simple molecular; copper: metallic; ethanol: simple molecular • Accept: “covalent” for simple molecular only if it is clear the substance is made of molecules. Reject: giant covalent. | 3 |
| 3(b) | the lithium atom loses one electron (from its outer shell) [1] Accept: Li → Li+ + e−. Reject: gains an electron; loses a proton. | 1 |
| 3(c) | • any two of: malleable (can be bent or hammered into shape); ductile (can be drawn into wires); conducts heat (good thermal conductor); high boiling point; sonorous • 1 mark each. Reject: conducts electricity; shiny; high melting point (these are in the table). Accept “high density” only if clearly stated for metals in general. | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 4(a) | carbon dioxide Accept: CO2. Reject: hydrogen. | 1 |
| 4(b) | calcium chloride Accept: CaCl2. Reject: calcium carbonate; calcium hydroxide. | 1 |
| 4(c) | neutralisation Reject: displacement; precipitation; decomposition. | 1 |
| 4(d) | • hydrogen ions (H+) react with the calcium carbonate / are used up • so the concentration of hydrogen ions decreases Reject: “the acid is used up” for the second mark with no reference to hydrogen ions; “hydroxide ions are added”. | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 5(a) | incorrect [1] The rate is higher, but the temperature is the same in both experiments, so the particles do not move faster. | 1 |
| 5(b) | incorrect [1] The acid is the limiting reactant. Experiment 2 has twice as many moles of acid, so it gives twice the volume of gas (150 cm3 and 300 cm3). | 1 |
| 5(c) | correct [1] A rise in temperature shows that heat energy is given out to the surroundings: exothermic. | 1 |
| 5(d) | • the acid in experiment 2 has more particles (hydrogen ions) per unit volume / a higher concentration of particles • so collisions between the particles are more frequent (higher collision frequency) • Reject: “more particles” with no reference to volume; “more collisions” without “frequent”; the particles move faster / have more energy. | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 6(a) | photosynthesis Reject: respiration; combustion. | 1 |
| 6(b) | unburnt hydrocarbons / soot (carbon particles) Reject: carbon dioxide; oxygen; water vapour; sulfur dioxide (the trees contain little sulfur); nitrogen oxides (not required). | 1 |
| 6(c) | cattle / cows / livestock (their digestion, belching) / rice (paddy) fields / decaying plant matter in wet fields Reject: burning fuels; car exhausts; volcanoes; “factories”. | 1 |
| 6(d) | it takes millions of years to form, so it cannot be replaced as fast as it is used / it will run out Reject: “it cannot be used again” with no reference to the time to form; “it is burnt”. | 1 |
| 6(e) | a compound that contains hydrogen and carbon only Reject: “a compound containing hydrogen and carbon” without “only”; a mixture of hydrogen and carbon. | 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. • 2Al(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2(g) • or NH4Cl(s) + NaOH(aq) → NaCl(aq) + H2O(l) + NH3(g) (accept NH4Cl(aq); the heating is not part of the equation) • or NH4Cl(aq) + AgNO3(aq) → AgCl(s) + NH4NO3(aq) (ionic: Ag+(aq) + Cl−(aq) → AgCl(s)) • or AlCl3(aq) + 3NaOH(aq) → Al(OH)3(s) + 3NaCl(aq) (ionic: Al3+(aq) + 3OH−(aq) → Al(OH)3(s)) • or AlCl3(aq) + 3NH3(aq) + 3H2O(l) → Al(OH)3(s) + 3NH4Cl(aq) (ionic: Al3+(aq) + 3NH3(aq) + 3H2O(l) → Al(OH)3(s) + 3NH4+(aq)) • ecf: an equation for a reaction in Fig. 7.1 that uses a substance wrongly identified in (a) earns the marks if its formulae, balancing and state symbols are correct for that substance. • The reaction in which the precipitate dissolves in excess aqueous sodium hydroxide is not required (the product is not on the syllabus); no mark for it. | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 8(a) | the sum of the relative atomic masses of all the atoms in the molecule (accept: average mass of a molecule compared with one-twelfth of the mass of an atom of carbon-12) Reject: “the mass of a molecule” with no comparison or no reference to atoms. | 1 |
| 8(b) | (2 × 1) + (2 × 16) = 34 | 1 |
| 8(c) | 68 ÷ 34 = 2.00 mol / dm3 (accept 2.0) (ecf from (b)) | 1 |
| 8(d) | 2.00 × 0.0500 dm3 = 0.100 mol (ecf from (c)); accept 68 × 0.0500 = 3.4 g, 3.4 ÷ 34 = 0.100 | 1 |
| 8(e) | 2 mol H2O2 form 1 mol O2: 0.100 ÷ 2 = 0.0500 mol [1]; 0.0500 × 24 = 1.20 dm3 [1] (ecf from (d)). Accept 1200 cm3. | 2 |
| 8(f) | 2 mol H2O2 form 2 mol H2O: 0.100 mol × 18 = 1.80 g (ecf from (d)) | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 9(a) | • B and C (both needed) [1] • their molecules contain a carbon–carbon double bond (C=C) [1] • Reject: “they have fewer hydrogen atoms” as the only reason; the reason with the wrong letters. | 2 |
| 9(b) | C3H6 Reject: CH3CH=CH2 (structural formula). | 1 |
| 9(c) | propane Reject: propene; the formula. | 1 |
| 9(d) | CnH2n+2 The series is the alkanes. Reject: CnH2n. | 1 |
| 9(e) | to match the demand for smaller molecules (more petrol) / crude oil has few or no alkenes (so alkenes must be made) / alkenes are needed to make polymers Reject: “to purify it”; “to separate the hydrocarbons”. | 1 |
| 9(f) | substitution Reject: addition; displacement; combustion. | 1 |
| 9(g) | C=C double bond [1]; two H atoms on one carbon and two F atoms on the other carbon [1]. Reject: a single bond between the carbon atoms; H and F mixed on the same carbon. | 2 |
| 9(h) | addition (polymerisation) Reject: condensation. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 10(a)(i) | reactivity increases down the group (the time taken to react decreases: 150 s, 40 s, 8 s). Accept: the metals react faster / more vigorously down the group. Reject: "decreases"; a statement about time only without a link to reactivity. | 1 |
| 10(a)(ii) | any value less than 8 s (and greater than 0 s). The value must be below the time for potassium, because the data show the times falling down the group. Reject: 8 s or more. | 1 |
| 10(b) | any one of: softer (can be cut with a knife); lower density (some float on water); lower melting point. Reject: "shiny"; "conduct electricity"; "reactive" (chemical, not physical). | 1 |
| 10(c) | • the elements change from metallic to non-metallic (character) from left to right / across the period • a contrasting pair of properties, one for each element (both needed), e.g. magnesium conducts electricity but sulfur does not; magnesium is malleable but sulfur is brittle; magnesium is shiny but sulfur is dull; magnesium has a high melting point but sulfur has a low melting point. Reject: a pair that does not contrast (e.g. "solid" for both); reactivity alone. | 2 |
| 10(d) | Rb2O. Reject: RbO; Rb2O2. (4Rb + O2 → 2Rb2O) | 1 |
| 10(e) | any one of: the potassium burns / catches fire / a lilac flame is seen; it moves faster / more quickly across the surface; the reaction is more vigorous / violent; the potassium melts (sodium may melt too, so accept only if a comparison is made). Reject: "bubbles of gas" alone; "potassium is more reactive" with no observation; "hydrogen is produced". | 1 |
| 10(f) | • lithium ion: [Li]+ in square brackets (or clearly an ion) with the charge +, and either no electrons (the outer shell is empty) or the two electrons of the first shell shown • chloride ion: [Cl]− in square brackets with the charge −, and eight electrons in its outer shell: seven of one symbol (from chlorine) and one of the other (from lithium) • Accept: both ions drawn with outer shell circles. Do not credit: a shared pair of electrons (covalent); Li+ with 1 electron; a missing or wrong charge loses the mark for that ion. | 2 |
| 10(g) | from 0 to +1 (both values needed). Accept: increases from 0 to +1. Reject: +1 to 0; "increases" with no values; 0 to −1. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 11(a) | • zinc heated strongly in air: reacts more quickly / more vigorously than lead (e.g. burns, glows, a white solid forms, surface becomes dull or covered with a white layer in a much shorter time). Reject: "no change"; a reaction slower than lead or no faster than lead • silver added to dilute hydrochloric acid: no bubbles / no reaction (silver is less reactive than copper, which gives no bubbles). Reject: any bubbles. | 2 |
| 11(b) | magnesium reacts faster / more vigorously (more bubbles / more quickly). Reject: "magnesium reacts" with no comparison; "slower / less vigorous". | 1 |
| 11(c)(i) | zinc chloride (accept ZnCl2; Zn + 2HCl → ZnCl2 + H2). Reject: zinc hydroxide; zinc oxide; zinc. | 1 |
| 11(c)(ii) | copper and silver are less reactive than hydrogen / are below hydrogen in the reactivity series (so they cannot displace hydrogen from the acid). Accept: they are not reactive enough. Reject: "they are unreactive" with no reference to hydrogen or acid, if the idea of position is absent. | 1 |
| 11(d) | lead and a reason: lead is less reactive than zinc (lower in the reactivity series / reacts less with acid and air in Table 11.1), so less energy is needed to obtain it from its oxide. Both the metal and the reason are needed. Accept: zinc holds on to oxygen more strongly. Reject: zinc, or lead with no reason or with "lead is more reactive". | 1 |
| 11(e) | calcium and a reason: calcium is more reactive than silver / is higher in the reactivity series (silver is below copper, which does not react with acid). Both the metal and the reason are needed. Reject: silver; calcium with no reason. | 1 |
| 11(f) | • two shared pairs of electrons, one between the oxygen atom and each hydrogen atom (each overlap has one dot and one cross); hydrogen has no other electrons • two non-bonding pairs (lone pairs) of electrons on oxygen, giving eight electrons in its outer shell • Accept: oxygen electrons all dots and hydrogen electrons all crosses (or the reverse). Do not credit: ions drawn (H+ and O2−); double bonds; hydrogen with more than two electrons. | 2 |
| 11(g) | gain (electrons), so oxygen is reduced. Both words needed. Reject: lose; oxidised. | 1 |