Relative masses of atoms and molecules: past paper questions
Real questions on relative masses of atoms and molecules
The newest 18 of 18 written questions. Open one to see it on the real paper.
- 0620/41 · October/November 2025 · Q2e(ii)[3]
When hydrated calcium nitrate is heated gently, the following reaction occurs. Ca(NO 3 ) 2 •xH 2 O Ca(NO 3 ) 2 + xH 2 O A sample of hydrated calcium nitrate is heated gently. 3.28 g of Ca(NO 3 ) 2 forms and the mass of the crystals decreases by 1.44 g. [M r : Ca(NO 3 ) 2 , 164; H 2 O, 18] Determine the value of x in Ca...
See it on the paper → - 0620/32 · May/June 2025 · Q3c[1]
A compound of phosphorus has the formula Ca 3 (PO 4 ) 2 . Complete Table 3.2 to calculate the relative formula mass of Ca 3 (PO 4 ) 2 . Table 3.2 atom number of atoms relative atomic mass oxygen 8 16 calcium 40 phosphorus 31 8 × 16 = 128
See it on the paper → - 0620/32 · February/March 2025 · Q8d[2]
Ethanoic acid has the formula CH 3 COOH. Complete Table 8.1 to calculate the relative molecular mass of CH 3 COOH. Table 8.1 type of atom number of atoms relative atomic mass carbon 2 12 hydrogen 1 oxygen 16 2 × 12 = 24 relative molecular mass =
See it on the paper → - 0620/33 · May/June 2024 · Q5d[2]
Another compound of phosphorus has the formula Na 3 PO 4 . Complete Table 5.1 to calculate the relative formula mass of Na 3 PO 4 . Table 5.1 type of atom number of atoms relative atomic mass sodium 3 23 phosphorus 31 oxygen 16 3 × 23 = 69 relative formula mass =
See it on the paper → - 0620/32 · February/March 2024 · Q2e(iii)[2]
Methylbutanoic acid has the molecular formula C 5 H 10 O 2 . Complete Table 2.2 to calculate the relative molecular mass of C 5 H 10 O 2 . Table 2.2 atom number of atoms relative atomic mass carbon 5 12 hydrogen 1 oxygen 16 5 × 12 = 60 relative molecular mass = [Total: 13]
See it on the paper → - 0620/42 · February/March 2024 · Q1b(i)[2]
Calculate the percentage by mass of iron in iron( III ) oxide, Fe 2 O 3 . percentage = %
See it on the paper → - 0620/32 · May/June 2023 · Q7f[2]
Ethanoic acid reacts with propanol. The organic product has the molecular formula C 5 H 10 O 2 . Complete Table 7.1 to calculate the relative molecular mass of C 5 H 10 O 2 . Table 7.1 atom number of atoms relative atomic mass carbon 12 hydrogen 1 oxygen 2 16 2 × 16 = 32 relative molecular mass = [Total: 13]
See it on the paper → - 0620/33 · May/June 2023 · Q7c[2]
Ethanol reacts to form a compound with the formula C 6 H 12 O 2 . Complete Table 7.1 to calculate the relative molecular mass of C 6 H 12 O 2 . Table 7.1 atom number of atoms relative atomic mass carbon 6 12 hydrogen 1 oxygen 16 6 × 12 = 72 relative molecular mass =
See it on the paper → - 0620/42 · February/March 2023 · Q1e(ii)[1]
Explain your answer to (i).
See it on the paper → - 0620/42 · February/March 2023 · Q3c(iii)[2]
Calculate the percentage composition by mass of nitrogen in (NH 4 ) 2 SO 4 . percentage of nitrogen = % [Total: 18]
See it on the paper → - 0620/11 · October/November 2022 · Q35[1]
What are the major uses of these fractions?
See it on the paper → - 0620/43 · May/June 2022 · Q5c[3]
The formula for crystals of hydrated copper( II ) sulfate is CuSO 4 •5H 2 O. Hydrated copper( II ) sulfate is made by reacting copper( II ) oxide with dilute sulfuric acid. The overall equation is shown. CuO + H 2 SO 4 + 4H 2 O → CuSO 4 •5H 2 O The crystals are made using the following steps: step 1 50.0 cm 3 of 0...
See it on the paper → - 0620/32 · February/March 2022 · Q8e[2]
A compound of chlorine has the formula C 3 H 6 Cl 2 . Complete the table to calculate the relative molecular mass of C 3 H 6 Cl 2 . atom number of atoms relative atomic mass carbon 3 12 hydrogen 1 chlorine 35.5 3 × 12 = 36 relative molecular mass = [Total: 12]
See it on the paper → - 0620/42 · February/March 2022 · Q3e[2]
135 moles of urea, (NH 2 ) 2 CO, is stored in the tank of a car. Calculate the mass, in kg, of the stored (NH 2 ) 2 CO. mass of (NH 2 ) 2 CO = kg
See it on the paper → - 0620/33 · October/November 2020 · Q4a(iii)[2]
Complete the table to calculate the relative molecular mass of crotonic acid. Use your Periodic Table to help you. type of atom number of atoms relative atomic mass carbon 4 12 hydrogen 1 oxygen 16 4 × 12 = 48 relative molecular mass =
See it on the paper → - 0620/42 · October/November 2020 · Q5d(iii)[2]
Calculate the percentage by mass of oxygen present in ethanediol. Give your answer to the nearest whole number. %
See it on the paper → - 0620/32 · February/March 2020 · Q4b[2]
The formula of ethanoic acid is C 2 H 4 O 2 . Complete the table to calculate the relative molecular mass of ethanoic acid. Use the Periodic Table to help you. type of atom number of atoms relative atomic mass carbon 2 12 2 × 12 = 24 hydrogen oxygen 16 relative molecular mass =
See it on the paper → - 0620/42 · February/March 2020 · Q3e[3]
PCl 5 reacts with lithium fluoride, LiF, to form LiPF 6 . PCl 5 + 6LiF → LiPF 6 + 5LiCl Calculate the mass of LiF needed to form 3.04 g of LiPF 6 using the following steps. ● ● Calculate the number of moles of LiPF 6 formed. [M r : LiPF 6 , 152] number of moles = ● ● Deduce the number of moles of LiF needed. n...
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What examiners said
Candidates struggled to calculate the relative formula mass of the given compound and there were many incorrect answers seen. Instead of using the number of atoms in the given formula, a lot of candidates used the atomic number of the element which gave, incorrectly, very big numbers for the answer.
— Examiner report, May/June 2025, 0620/32 Q3(c) (Cambridge)
Most candidates were able to calculate the relative molecular mass of ethanoic acid correctly. Common incorrect answers included 58 and 59 where candidates had incorrectly interpreted the number of hydrogens in the formula.
— Examiner report, February/March 2025, 0620/32 Q8(d) (Cambridge)
Most candidates were able to calculate the relative molecular mass of the organic acid correctly.
— Examiner report, February/March 2024, 0620/32 Q2(e)(iii) (Cambridge)
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