The mole and the Avogadro constant: past paper questions
Real questions on the mole and the avogadro constant
The newest 20 of 159 written questions. Open one to see it on the real paper.
- 5070/21 · October/November 2025 · Q3c[3]
A sample of sodium hydrogencarbonate is completely decomposed. A total volume of 230 cm 3 of carbon dioxide, measured at r.t.p., is produced. Calculate the mass of the sample of sodium hydrogencarbonate. Give your answer to two significant figures. mass of sodium hydrogencarbonate = g
See it on the paper → - 5070/22 · October/November 2025 · Q3c[3]
A sample of aluminium reacts completely with dilute hydrochloric acid. A total volume of 366 cm 3 of hydrogen, measured at r.t.p., is produced. Calculate the mass of the sample of aluminium. Give your answer to two significant figures. mass of aluminium = g
See it on the paper → - 5070/22 · October/November 2025 · Q6b(i)[2]
Calculate the number of molecules of hydrogen peroxide in this sample. One mole of hydrogen peroxide contains 6.02 × 10 23 molecules. number of molecules =
See it on the paper → - 5070/22 · October/November 2025 · Q6b(ii)[1]
Calculate the total number of atoms in this sample of hydrogen peroxide. number of atoms =
See it on the paper → - 5070/41 · October/November 2025 · Q2d[1]
X is 1.60 mol / dm 3 sodium hydroxide solution. The formula of sodium hydroxide is NaOH. Calculate the number of moles of hydroxide ions, OH – , in 25.0 cm 3 of X. number of moles
See it on the paper → - 5070/41 · October/November 2025 · Q2e[1]
The volume of Y in (c) is the volume needed to completely neutralise 25.0 cm 3 of X. Use your answers to (c) and (d) to calculate the concentration of hydrogen ions, H + , in Y. H + + OH – H 2 O concentration mol / dm 3
See it on the paper → - 5070/42 · October/November 2025 · Q2d[1]
Y is 2.0 mol / dm 3 potassium hydroxide. The formula of potassium hydroxide is KOH. Calculate the number of moles of hydroxide ions, OH – , in the volume of Y in (c). number of moles
See it on the paper → - 5070/42 · October/November 2025 · Q2e[1]
The volume of Y in (c) is the volume needed to completely neutralise 25.0 cm 3 of X. Use your answer to (d) to calculate the concentration of hydrogen ions, H + , in X. H 2 O concentration mol / dm 3 H + + OH –
See it on the paper → - 5070/21 · May/June 2025 · Q6b[2]
A sample of chlorine gas contains 1.204 × 10 20 molecules. One mole of chlorine gas contains 6.02 × 10 23 molecules. Calculate the mass of this sample of chlorine gas. mass of chlorine = g
See it on the paper → - 5070/22 · May/June 2025 · Q4c(ii)[3]
A sample of 1.35 g of calcium is added to excess dilute ethanoic acid. Calculate the volume of hydrogen formed measured at room temperature and pressure. Give your answer to two significant figures. volume = dm 3 (ii)
See it on the paper → - 5070/22 · May/June 2025 · Q6b[2]
A sample of bromine liquid contains 2.408 × 10 25 molecules. One mole of bromine liquid contains 6.02 × 10 23 molecules. Calculate the mass of this sample of bromine liquid. mass of sample = g
See it on the paper → - 5070/41 · May/June 2025 · Q2a[1]
The student: • • • • places the sample of A into a beaker uses a measuring cylinder to add 100 cm 3 of 0.250 mol / dm 3 hydrochloric acid, HCl, to the beaker stirs the mixture until no further effervescence is observed labels the mixture B. Calculate the number of moles of HCl added to the beaker. number of moles
See it on the paper → - 5070/41 · May/June 2025 · Q2f[1]
The equation for the reaction between hydrochloric acid and calcium carbonate is shown. 2HCl + CaCO 3 CaCl 2 + H 2 O + CO 2 Calculate the number of moles of calcium carbonate in the sample of A. number of moles (f)
See it on the paper → - 5070/42 · May/June 2025 · Q2c[1]
Calculate the number of moles of NaOH in 25 cm 3 of 0.100 mol / dm 3 NaOH. number of moles
See it on the paper → - 5070/42 · May/June 2025 · Q2d[1]
The equation for the reaction between H 3 A and NaOH is shown. H 3 A + 3NaOH Na 3 A + 3H 2 O Calculate the number of moles of H 3 A that react with 25.0 cm 3 of 0.100 mol / dm 3 NaOH. number of moles
See it on the paper → - 5070/42 · May/June 2025 · Q2e[1]
Calculate the number of moles of H 3 A in the sample of W. number of moles
See it on the paper → - 5070/42 · May/June 2025 · Q2f[1]
The relative molecular mass of H 3 A is 210. Calculate the mass of H 3 A in the sample of W. mass g
See it on the paper → - 5070/22 · October/November 2024 · Q6e[3]
Boron oxide reacts with magnesium as shown. B 2 O 3 + 3Mg 2B + 3MgO Show by calculation that boron oxide is in excess. 8.0 g of boron oxide is reacted with 7.2 g of magnesium.
See it on the paper → - 5070/41 · October/November 2024 · Q2d[1]
Calculate the number of moles of NaOH in 25.0 cm 3 of 0.800 mol / dm 3 NaOH(aq). number of moles
See it on the paper → - 5070/41 · October/November 2024 · Q2e[3]
One mole of ethanedioic acid is neutralised by two moles of sodium hydroxide. Use your answers to (c) and (d) to calculate the concentration, in mol / dm 3 , of ethanedioic acid. Give your answer to three significant figures. concentration mol / dm 3
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What examiners said
Candidates found this equation very challenging. Most did not include oxygen as a reactant or gave the formula as O. Copper was often Cu2. Common products included CuO and Cu2SO4.
— Examiner report, October/November 2023, 5070/21 Q2(e) (Cambridge)
Almost all candidates read the graph correctly. A small number gave 50 seconds.
— Examiner report, October/November 2023, 5070/21 Q3(b)(i) (Cambridge)
Candidates found this quite challenging. Many gave less steep lines, with the final volume often greater or sometimes smaller than the original. A small number omitted the question.
— Examiner report, October/November 2023, 5070/21 Q3(b)(ii) (Cambridge)
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