plumiRelative masses, molar mass, ppm and concentration: Edexcel International A Level Chemistry questions
Edexcel International A Level Chemistry past-paper questions on 1.1.4 Relative masses, molar mass, ppm and concentration, 2019–2025, with mark schemes and examiner’s reports where available.
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All 87 questions on Relative masses, molar mass, ppm and concentration, as a list
- June 2025, AS Unit 1, Q3 (1 mark): Which amount does not have a mass of approximately 6 g? A 0.33 mol water (H2O; Mr = 18) B 0.25 mol magnesium (Mg; Ar = 24.3) C 0.033 mol glucose (C6H12O6 ; Mr =
- June 2025, AS Unit 1, Q5 (1 mark): Which mass of fertiliser contains 467 g of nitrogen? A 2 kg sodium nitrate (NaNO3 ; Mr = 85) B 1 kg urea (NH2CONH2 ; Mr = 60) C 1 kg ammonium nitrate (NH4NO3 ;
- June 2025, AS Unit 1, Q20(a) (4 marks): According to data from 2021, there are 415 ppm of carbon dioxide in the atmosphere by volume. Calculate the moles of carbon dioxide present in 1.00 m3 of air at
- June 2025, Unit 5, Q11(d) (1 mark): What is the percentage of carbon, by mass, in the final product? (1) [Mr of the final product = 165] A 58.2% B 65.5% C 72.7% D 80.0%
- June 2025, Unit 5, Q17(b) (2 marks): When trimethylamine oxidises, it forms trimethylamine N-oxide, C3H9NO. −6 mol dm −3 Healthy humans have a concentration of 3.90 × 10 trimethylamine N-oxide in t
- June 2025, Unit 5, Q20(e) (2 marks): 5-Nitrosalicylic acid has a solubility of 1 g in 1475 cm –3. Calculate the concentration of a saturated solution in mol dm (2) [5-nitrosalicylic acid Mr = 183]
- June 2025, Unit 6, Q1(a)(iv) (2 marks): Give the formula of salt A, which has a molar mass of 197.9 g mol–1. (2)
- June 2025 (A), Unit 5, Q1(b) (1 mark): The solution for the right‑hand half‑cell is prepared by adding suitable amounts of iron(II) sulfate and iron(III) sulfate to distilled water to make 1.00 dm3 o
- June 2025 (A), Unit 5, Q16(c)(iii) (4 marks): Calculate the concentration of dissolved oxygen, in ppm, in the sample collected. [Assume the density of water = 1.0 g cm–3] (4)
- January 2025, AS Unit 1, Q2 (1 mark): How many moles of ions are there in 40 cm3 of a solution of 0.050 mol dm–3 magnesium nitrate, Mg(NO3)2? A 0.0020 mol B 0.0040 mol C 0.0060 mol D 0.0080 mol
- January 2025, AS Unit 1, Q4 (1 mark): NxO4 is an oxide of nitrogen. The percentage by mass of oxygen in this oxide is 69.57%. What is the relative molecular mass of this oxide? A 78 B 92 C 106 D 109
- January 2025, AS Unit 1, Q5 (1 mark): Four different solutions contain chloride ions. Three of the solutions contain the same number of moles of chloride ions. Which solution contains a different nu
- January 2025, AS Unit 1, Q6 (1 mark): A solution contains 95 ppm of a solute. What mass of the solute is dissolved in 1 kg of this solution? A 95 g B 0.95 g C 0.095 g D 0.000095 g
- January 2025, AS Unit 2, Q3 (1 mark): 20 cm3 of a saturated solution of barium nitrate at 80 °C was cooled to 20 °C. 9.32 g of crystals were precipitated. The solubility of barium nitrate is 3.74 g
- January 2025, AS Unit 2, Q14 (1 mark): What is the concentration, in mol dm–3 , when 64.5 g of sodium nitrate is dissolved in water to form 750 cm3 of solution? [Mr NaNO3 = 85.0] A 0.086 B 0.113 C 0.
- January 2025, Unit 4, Q20(e)(ii) (3 marks): A 0.558 mol dm−3 solution of oxalic acid is used for cleaning. Calculate the mass of spinach required to make 500 cm3 of this oxalic acid cleaning solution. [Da
- January 2025, Unit 5, Q20(c)(i) (2 marks): Show, by calculation, that the Cr3+ level in this blood sample exceeds the safe limit. [1 billion = 1 × 109 Assume the density of blood is 1.0 g cm–3] (2)
- October 2024, AS Unit 1, Q17(b) (2 marks): Sodium hydroxide also forms a heptahydrate, NaOH•7H2O. Calculate the mass of this heptahydrate needed to make 250 cm3 of a solution of sodium hydroxide of conce
- October 2024, AS Unit 2, Q18(b) (1 mark): Each molecule of X contains carbon atoms, hydrogen atoms, and one atom of oxygen. Identify X, by name or formula, using your answer from (a). (1)
- October 2024, Unit 5, Q3 (1 mark): The formula of a chromium compound is [Cr(H2O)4Cl2]+Cl– . The molar mass of the compound is 230.5 g mol−1. What is the percentage by mass of chlorine in the com
- October 2024, Unit 5, Q15(b) (2 marks): Butylamine has a fishy, ammonia-like smell. The exposure limit or safety level in the atmosphere for butylamine is 15 mg m−3 . Calculate the maximum number of b
- October 2024, Unit 5, Q18(c)(ii) (2 marks): 50.0 cm3 of a solution of copper(II) sulfate of unknown concentration was pipetted into a 250.0 cm3 volumetric flask and the volume made up to the mark with dei
- June 2024, AS Unit 1, Q16(a)(i) (2 marks): Define relative atomic mass. (2)
- June 2024, Unit 5, Q16(b)(iii) (3 marks): When a 5 dm3 sample of wastewater was treated with excess acidified sodium dimethyldithiocarbamate, 245.0 mg of the dry precipitate H+[Ni((CH3)2NCS2)3]− was for
- June 2024, Unit 5, Q19(b)(ii) (2 marks): Use your structure from 19(b)(i) to calculate the percentage of hydroxyl groups by mass in the polymer. (2)
- June 2024, Unit 5, Q19(c)(iii) (4 marks): Glycerol is added to the polymer at 0.110%, by volume. Calculate the number of moles of glycerol added to 1 tonne of poly(ethenol). Data: 1 tonne = 1000 kg dens
- June 2024, Unit 6, Q5(b)(ii) (2 marks): Identify the halide X, present in NH4X, using your answer to (b)(i). (2)
- June 2024 (R), AS Unit 2, Q19(c) (2 marks): Ozone can also be used in the treatment of water in swimming pools. A swimming pool has a volume of 375 000 dm3 and contains 15 g of ozone. Calculate the concen
- June 2024 (R), AS Unit 2, Q22(b)(i) (1 mark): Complete the table by calculating the percentage by mass of nitrogen in ammonium nitrate. (1)
- June 2024 (R), AS Unit 2, Q22(b)(ii) (2 marks): Give one advantage and one disadvantage of applying ammonia directly into the soil as a fertiliser. Use information in the table and your knowledge of ammonia.
- January 2024, AS Unit 1, Q6 (1 mark): Which oxide of nitrogen contains 30% nitrogen by mass? [Ar values: N = 14.0 O = 16.0] A NO B NO2 C N2O D N2O3
- January 2024, AS Unit 1, Q7 (1 mark): Calculate the mass of sodium carbonate (Na2CO3) required to make up 250 cm3 of a 0.100 mol dm−3 solution. [Ar values: C = 12.0 O = 16.0 Na = 23.0] A 1.30 g B 2.
- January 2024, AS Unit 1, Q13 (1 mark): The concentration of sulfur dioxide in a sample of polluted air is 0.4 ppm. What is the percentage of sulfur dioxide molecules in this polluted air? A 0.4% B 0.
- January 2024, AS Unit 2, Q24(c) (2 marks): The structure of a fire retardant is shown. Br Br Br Br Br Br Calculate the percentage by mass of bromine in this fire retardant. Give your answer to an appropr
- January 2024, Unit 5, Q1(b) (1 mark): A student wishes to measure the standard cell potential, Ecell , of this cell. The right‑hand cell requires Cr3+ and Cr2+ ions. What mass of Cr2(SO4)3·18H2O mus
- October 2023, AS Unit 1, Q12(a) (1 mark): A sample of a gaseous mixture contains 2.19 % carbon dioxide by mass. What is the concentration of carbon dioxide in parts per million (ppm) by mass in this sam
- October 2023, AS Unit 1, Q12(b) (1 mark): A solution of lead nitrate has a concentration of 15 ppm by mass. What is the mass of lead nitrate in 400 g of this solution? (1) A 6.00 × 10–3 g B 6.00 × 10–6
- October 2023, AS Unit 1, Q13 (1 mark): Which solution contains chloride ions with a concentration of 0.0500 mol dm–3? [Ar values: Ca = 40.1 Cl = 35.5 Na = 23.0] Volume of solution / cm3 Solute Mass o
- October 2023, AS Unit 1, Q20(d)(ii) (2 marks): A sample of polyisoprene has a relative molecular mass of 50 250. Calculate the number of repeat units in the sample. (2)
- October 2023, AS Unit 1, Q21(a)(i) (1 mark): Calculate the relative formula mass of basic nickel(II) carbonate, Ni3CO3(OH)4 • 4H2O. (1)
- October 2023, AS Unit 1, Q21(a)(iii) (1 mark): Give the reason why use of the term ‘relative molecular mass’ is not appropriate in (a)(i). (1)
- June 2023, AS Unit 2, Q11 (1 mark): A piece of sodium weighing 1.15 g reacts completely with distilled water and the solution formed is made up to 250.0 cm3. 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) W
- January 2023, AS Unit 1, Q2 (1 mark): What is the concentration of hydroxide ions in a solution containing 5.00 g of Ba(OH)2 in 250 cm3? [Mr Ba(OH)2 = 171.3] A 0.0292 mol dm–3 B 0.0584 mol dm–3 C 0.
- January 2023, AS Unit 2, Q18(c)(i) (3 marks): Calculate the mass, in kg, of Ca(ClO)2 required to treat the water needed to completely fill this swimming pool. (3)
- January 2023, Unit 5, Q5 (1 mark): The formula of hydrated copper(II) bromide is CuBr2·4H2O. What is the percentage, by mass, of water of crystallisation in this compound? A 6.10 % B 8.06 % C 24.
- January 2023, Unit 5, Q10 (1 mark): A sample of air contains 405 parts per million (ppm) of carbon dioxide. What is the approximate volume, in cm3 , of carbon dioxide in 250 cm3 of this air? A 0.0
- October 2022, AS Unit 1, Q12 (1 mark): A mass of 4.08 g of hydrated copper(II) sulfate, CuSO4∙5H2O, was dissolved in deionised water to form 250 cm3 of solution. What is the concentration of the copp
- October 2022, AS Unit 1, Q14(b)(ii) (2 marks): Calculate the mass of barium chloride needed to form 150 cm3 of BaCl2(aq) with a concentration of 0.200 mol dm–3. Give your answer to an appropriate number of s
- October 2022, AS Unit 1, Q16(e)(iv) (2 marks): Calculate the molar mass of GeX4 and hence identify X. (2)
- October 2022, AS Unit 2, Q21(c) (2 marks): Dilute sulfuric acid is used in many laboratories. It is often supplied as concentrated sulfuric acid and then diluted. A technician makes 500 cm3 of 1.5 mol dm
- October 2022, AS Unit 3, Q3(b)(ii) (1 mark): Calculate the number of moles of potassium iodide in each test tube. (1)
- October 2022, AS Unit 3, Q3(b)(iii) (1 mark): Calculate the concentration of the metal nitrate solution in g dm−3 using the information given in the procedure. (1)
- October 2022, AS Unit 3, Q3(b)(iv) (4 marks): Identify X by using your answers to (b)(i), (b)(ii) and (b)(iii) to determine the Mr of the metal nitrate. You must show all your working. (4)
- October 2022, Unit 5, Q22(a) (4 marks): Viridian is a blue‑green pigment with the formula M2O3·2H2O ; M is not the symbol of the element. When a sample of viridian is heated until all the water of cry
- June 2022, AS Unit 1, Q4 (1 mark): A solution of sodium chloride, NaCl, is prepared by dissolving 10.0 g of the solid in distilled water and making the solution up to 250.0 cm3. What is the conce
- June 2022, AS Unit 1, Q19(a)(ii) (2 marks): Calculate the number of moles of iron(III) chloride that react. (2)
- June 2022, Unit 6, Q4(b)(iii) (3 marks): A student obtained 1.20 cm3 of limonene. Calculate the amount, in moles, of limonene produced. (3)
- January 2022, AS Unit 1, Q9 (1 mark): The concentration of nitrogen dioxide in a sample of air is 0.5 ppm. What is the percentage of nitrogen dioxide molecules in this sample of air? A 0.5 % B 0.005
- January 2022, AS Unit 1, Q17 (1 mark): Which of these solutions contains the greatest number of ions? A 20.0 cm3 of 0.5 mol dm−3 KCl B 0.40 dm3 of 0.03 mol dm−3 KCl C 10.0 cm3 of 0.6 mol dm−3 CaCl2 D
- January 2022, AS Unit 2, Q24(b) (2 marks): A saturated solution of urea has a concentration of 9.07 mol dm–3 at 25 °C. Calculate the mass of urea in 150 cm3 of a saturated solution. (2)
- January 2022, Unit 5, Q4 (1 mark): A mass of 4.179 g of hydrated iron(III) sulfate, Fe2(SO4)3·H2O , was dissolved in deionised water and the solution made up to 200 cm3. 2− , in the solution, in
- October 2021, AS Unit 1, Q1(a) (1 mark): What is this concentration of sulfur in ppm? (1) A 0.00001 B 0.01 C 10 D 10 000
- October 2021, AS Unit 1, Q4(a) (1 mark): What is the concentration, in mol dm−3, of sodium hydroxide in the solution formed? (1) A 0.010 B 0.029 C 0.29 D 0.66
- October 2021, AS Unit 1, Q7(a) (1 mark): What is the relative formula mass of the double salt? [Ar values: H = 1.0 N = 14.0 O = 16.0 S = 32.1 Fe = 55.8] (1) A 277.9 B 284.0 C 392.0 D 447.8
- October 2021, AS Unit 2, Q13 (1 mark): A student is provided with 25.0 cm3 of 1.00 mol dm–3 hydrochloric acid. What volume of distilled water should the student add to this solution to make a 0.0500
- June 2021, AS Unit 1, Q7 (1 mark): What is the relative formula mass of hydrated sodium carbonate, Na2CO3. 10H2O? [Ar values: H = 1.0 C = 12.0 O = 16.0 Na = 23.0] A 106 B 142 C 263 D 286
- June 2021, AS Unit 1, Q19 (1 mark): Which aqueous solution contains the greatest number of ions? A 200 cm3 of 1.5 mol dm−3 MgCl2 B 400 cm3 of 0.8 mol dm−3 MgSO4 C 500 cm3 of 1.0 mol dm−3 NaCl D 10
- June 2021, AS Unit 2, Q14 (1 mark): A 4.00 mol dm−3 solution of an acid is used to prepare dilute solutions of the acid. What volume of water is required to make up 150 cm3 of 0.35 mol dm−3 soluti
- June 2021, AS Unit 2, Q15(a) (1 mark): A pellet of sodium hydroxide has a mass of 0.700 g. Some pellets were dissolved to make 350 cm3 of 0.25 mol dm–3 solution. [Mr value: NaOH = 40] How many pellet
- June 2021, Unit 5, Q21(d)(i) (4 marks): The presence of iron in sodium carbonate can affect its properties; the higher the quality of the sodium carbonate, the lower the proportion of iron. The propor
- January 2021, AS Unit 1, Q3 (1 mark): Which aqueous solution has the highest concentration, in mol dm-3, of chloride ions? A 0.1 g dm-3 HCl B 0.1 g dm-3 NaCl C 0.1 g dm-3 KCl D 0.1 g dm-3 BaCl2
- January 2021, AS Unit 1, Q21(c)(ii) (1 mark): Squalane used in cosmetic products must contain no more than 0.2 ppm by mass of catalyst. Calculate the maximum permitted mass of catalyst in a product containi
- January 2021, AS Unit 2, Q21(d) (2 marks): Ammonium carbonate, (NH4)2CO3 , is an ingredient in cleaning solutions for camera lenses. These are aqueous solutions which contain no more than 1.8 g of ammoni
- January 2021, Unit 4, Q18(b)(i) (2 marks): Commercial concentrated sulfuric acid contains 98.5 % H2SO4 and 1.5 % water by mass. The density of concentrated sulfuric acid is 1800 g dm−3. Calculate the con
- January 2021, Unit 5, Q24(b)(i) (4 marks): Calculate the concentration, in mol dm−3, of caffeine in this cup of coffee. Give your answer to an appropriate number of significant figures. (4)
- October 2020, AS Unit 1, Q5 (1 mark): The formula of barium chloride is BaCl2. Which is correct for barium chloride? [ Ar values: Ba = 137.3 Cl = 35.5 ] A barium chloride exists as a molecule B bari
- October 2020, AS Unit 1, Q21(c)(i) (1 mark): State the meaning of ppm. (1)
- October 2020, AS Unit 1, Q21(c)(ii) (3 marks): A sample of 3.25 cm3 of bromine vapour leaks into a laboratory. Calculate the minimum volume, in dm3, of the laboratory for the resulting concentration of bromi
- October 2020, Unit 5, Q20 (1 mark): A solution contains 19.6 g dm−3 of chromium(III) sulfate, Cr2(SO4)3 . What is the concentration, in mol dm–3, of sulfate ions in this solution? [Molar mass Cr2(
- January 2020, AS Unit 1, Q6 (1 mark): What is the relative formula mass of hydrated barium hydroxide, Ba(OH)2.8H2O? [Ar values: Ba = 137.3, O = 16.0, H = 1.0] A 171.3 B 203.3 C 299.3 D 315.3
- January 2020, AS Unit 1, Q7 (1 mark): An 11.0 g sample of anhydrous sodium sulfate, Na2SO4 , is dissolved in deionised water to form 70 cm3 of solution. What is the concentration, in mol dm–3, of Na
- January 2020, AS Unit 1, Q20(b)(iv) (3 marks): Calculate the percentage by mass of bromine in the heaviest molecule containing six carbon atoms that could form when hexane reacts with a large excess of bromi
- January 2020, AS Unit 1, Q21(b) (5 marks): Ethene is used commercially to speed up the ripening of bananas. Ethene levels of 100 parts per million (ppm) are used in ripening rooms. Calculate the amount,
- January 2020, AS Unit 2, Q18(a) (2 marks): Calculate the percentage by mass of nitrogen in urea. (2)
- June 2019, AS Unit 1, Q7 (1 mark): Which isotope is used as the standard in the definition of relative atomic mass? 1H A 12C B 13C C 16O D
- January 2019, AS Unit 1, Q18 (1 mark): What mass of anhydrous sodium carbonate is needed to make 50.0 cm3 of a 0.0800 mol dm−3 solution of sodium carbonate, Na2CO3? [Ar values: C = 12.0, O = 16.0, Na
- January 2019, AS Unit 1, Q19 (1 mark): A sample of air, with a mass of 5.0 kg, contained carbon monoxide with a concentration of 12 parts per million by mass. What is the mass of carbon monoxide in t
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