Stoichiometry: past paper questions
Real questions on stoichiometry
The newest 20 of 45 written questions, plus 17 multiple-choice. Open one to see it on the real paper.
- 5129/21 · October/November 2025 · Q2c(i)[1]
The relative atomic masses, A r , of calcium and nitrogen are shown. [A r : Ca, 40; N, 14] M r = Calculate the relative formula mass, M r , of calcium nitride, Ca 3 N 2 .
See it on the paper → - 5129/22 · October/November 2025 · Q2b(i)[1]
Complete the following sentence. 7.8 g of potassium reacts with g of oxygen.
See it on the paper → - 5129/22 · October/November 2025 · Q8e[1]
incomplete combustion
See it on the paper → - 5129/21 · May/June 2025 · Q5c[1]
g of silver nitrate is dissolved in 200 cm 3 of distilled water. Calculate the concentration of the solution. [1 dm 3 = 1000 cm 3 ] concentration = g / dm 3
See it on the paper → - 5129/22 · May/June 2025 · Q5b[1]
Calculate the relative formula mass M r of sodium sulfate, Na 2 SO 4 . The relative atomic masses, A r , of oxygen, sodium and sulfur are shown. [A r : O, 16; Na, 23; S, 32] M r =
See it on the paper → - 5129/21 · October/November 2024 · Q3a(i)[1]
Calculate the relative molecular mass M r of phosphorus( V ) oxide. M r = [A r : O, 16; P, 31] The relative atomic masses, A r , of phosphorus and oxygen are shown.
See it on the paper → - 5129/21 · October/November 2024 · Q3a(ii)[1]
Complete the following sentence. 62 g of phosphorus reacts with g of oxygen. (ii)
See it on the paper → - 5129/21 · October/November 2024 · Q3b(i)[1]
Balance the symbol equation for the reaction. P 4 O 10 + H 2 O H 3 PO 4
See it on the paper → - 5129/21 · October/November 2024 · Q3b(ii)[2]
Suggest the pH of the contents of the conical flask before and after the phosphorus( V ) oxide is added. pH before
See it on the paper → - 5129/21 · October/November 2024 · Q3b(iii)[1]
g of phosphoric acid is dissolved in 250 cm 3 of distilled water. Calculate the concentration of the solution. [1 dm 3 = 1000 cm 3 ] concentration = g / dm 3
See it on the paper → - 5129/22 · October/November 2024 · Q3b(i)[1]
Calculate the relative molecular mass M r of sulfuric acid. The relative atomic masses, A r , of hydrogen, oxygen and sulfur are shown. [A r : H, 1; O, 16; S, 32] M r =
See it on the paper → - 5129/22 · October/November 2024 · Q3b(ii)[1]
Complete the following sentence. 4 g of sulfur trioxide reacts with g of water.
See it on the paper → - 5129/21 · May/June 2024 · Q3a(i)[1]
Calculate the relative molecular mass M r of chloric( I ) acid. M r =
See it on the paper → - 5129/21 · May/June 2024 · Q3a(ii)[1]
Complete the following sentence. 142 g of chlorine reacts with g of water.
See it on the paper → - 5129/21 · May/June 2024 · Q3b[1]
State the colour of chlorine gas at room temperature and pressure.
See it on the paper → - 5129/21 · May/June 2024 · Q3c[2]
Describe a test and the result of the test that shows the presence of chlorine. test result
See it on the paper → - 5129/22 · May/June 2024 · Q3a(i)[1]
Calculate the relative molecular mass M r of sodium bromate(I). M r =
See it on the paper → - 5129/22 · May/June 2024 · Q3a(ii)[1]
Complete the following sentence. 160 g of bromine produces g of sodium bromide.
See it on the paper → - 5129/22 · October/November 2023 · Q3a(i)[1]
Calculate the relative molecular mass M r of methanol. M r =
See it on the paper → - 5129/22 · October/November 2023 · Q3a(ii)[2]
Complete the following sentences. g of carbon monoxide produces 160 g of methanol. g of hydrogen produces 6.4 g of methanol.
See it on the paper →
What examiners said
Only the most able candidates were able to apply the ratio of the reacting molecules to determine the correct reacting masses.
— Examiner report, October/November 2023, 5129/22 Q3(a)(ii) (Cambridge)
Candidates recognised that 19 g is one-tenth of the answer to (a)(i) and used the equation to calculate 4.8 g of Mg (one-tenth of 2 moles × 24) and one-tenth of 48 g of tin (also 4.8).
— Examiner report, May/June 2023, 5129/21 Q3(a)(ii) (Cambridge)
Only the strongest candidates determined the correct concentration. This is an example of proportional reasoning. If 100 cm3 has 2 g, then 10 × the volume (1000 cm3) has (10 × 2 =) 20 g / dm3.
— Examiner report, May/June 2023, 5129/21 Q15(a)(iii) (Cambridge)
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