Atoms, molecules and stoichiometry: past paper questions

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• Question 3May/June 2026, paper 11Multiple choice1 mark

  Which statement is correct?

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• Question 3Oct/Nov 2025, paper 11Multiple choice1 mark

  What contains $9.03\times {10}^{23}$ oxygen atoms?

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• Question 3Oct/Nov 2024, paper 11Multiple choice1 mark

  Glauber’s salt consists of crystals of hydrated sodium sulfate, ${\text{Na}}_2{\text{SO}}_4\cdot x{\text{H}}_2\text{O}$, which can be used for the manufacture of detergents.

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• Question 3Oct/Nov 2023, paper 11Multiple choice1 mark

  Aluminium carbide, ${\mathrm{A}\mathrm{l}}_4{\mathrm{C}}_3$, reacts readily with aqueous sodium hydroxide. The two products of the reaction are ${\mathrm{N}\mathrm{a}\mathrm{A}\mathrm{l}\mathrm{O}}_2$ and a hydrocarbon. Water molecules are also involved as reactants.

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• Question 4May/June 2026, paper 11Multiple choice1 mark

  Which sample of gas has the smallest volume at room conditions?

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• Question 4Oct/Nov 2025, paper 11Multiple choice1 mark

  Methane and steam react to produce hydrogen. $${\text{CH}}_4(\text{g})+2{\text{H}}_2\text{O}(\text{g})\to {\text{CO}}_2(\text{g})+4{\text{H}}_2(\text{g})$$ $0.80\text{ g}$ of methane and $1.35\text{ g}$ of steam react. One of the reactants is used up.

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• Question 4Oct/Nov 2024, paper 11Multiple choice1 mark

  What contains the greatest number of the named particles?

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• Question 11May/June 2026, paper 11Multiple choice1 markHas a diagram

  The equation for the reaction between nitric acid and arsenous acid, ${\text{H}}_3{\text{AsO}}_3$, is shown. $$x{\text{HNO}}_3+y{\text{H}}_3{\text{AsO}}_3\to x\text{NO}+y{\text{H}}_3{\text{AsO}}_4+z{\text{H}}_2\text{O}$$ What are the numerical values of $x$ and $y$?

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• Question 17Oct/Nov 2025, paper 11Multiple choice1 mark

  Three equations are listed. $x$, $y$ and $z$ are all whole numbers.

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• Question 17Oct/Nov 2024, paper 11Multiple choice1 markHas a diagram

  Elements X and Y are in Period 3 of the Periodic Table. Element X is either phosphorus or sulfur. Element Y is either sodium or magnesium.

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• Question 12May/June 2026, paper 11Multiple choice1 mark

  Nitrogen dioxide dissociates according to the equation shown.

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• Question 20Oct/Nov 2025, paper 11Multiple choice1 mark

  Equal masses of ${\text{CaCO}}_3$, ${\text{Ca(NO}}_3{)}_2$, ${\text{BaCO}}_3$ and ${\text{Ba(NO}}_3{)}_2$ are thermally decomposed. The volume of gas produced in each experiment is measured under the same conditions. Which compound will produce the greatest volume of gas?

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• Question 23Oct/Nov 2024, paper 11Multiple choice1 mark

  $7.5\text{ g}$ of nitrogen monoxide reacts with $7.0\text{ g}$ of carbon monoxide on the surface of the catalytic converter in the exhaust system of a car. What is the total volume of the product gases measured at room conditions?

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• Question 24Oct/Nov 2023, paper 11Multiple choice1 mark

  If ammonium cyanate is heated in the absence of air, the only product of the reaction is urea, $\mathrm{C}\mathrm{O}({\mathrm{N}\mathrm{H}}_2{)}_2$. No other products are formed in the reaction. What is the formula of the cyanate ion present in ammonium cyanate?

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• Question 19May/June 2026, paper 11Multiple choice1 mark

  Which reaction produces the smallest total number of moles of gas?

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• Question 30Oct/Nov 2024, paper 11Multiple choice1 markHas a diagram

  The structure of limonene is shown. What are the number of moles of carbon dioxide and water produced when a sample of limonene is completely combusted in oxygen?

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• Question 25Oct/Nov 2023, paper 11Multiple choice1 markHas a diagram

  Hexamine is a crystalline solid used as a fuel in portable stoves. The diagram shows its skeletal structure. What is the empirical formula of hexamine?

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• Question 26May/June 2026, paper 11Multiple choice1 mark

  Which compound has the empirical formula ${\text{CH}}_2\text{O}$?

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• Question 3Oct/Nov 2025, paper 12Multiple choice1 mark

  The reaction of hydrogen sulfide with sulfur dioxide gives sulfur as one of the products. The two relevant redox equations are shown.

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• Question 3Oct/Nov 2023, paper 12Multiple choice1 mark

  Zinc reacts with concentrated nitric acid giving three products only: zinc nitrate, an oxide of nitrogen and water. $3.0\text{ moles}$ of zinc react with $8.0\text{ moles}$ of nitric acid. Zinc nitrate contains ${\text{Zn}}^{2+}$ ions.

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• Question 37Oct/Nov 2024, paper 12Multiple choice1 markHas a diagram

  A sample of propanoic acid of mass $3.70\text{ g}$ reacts with an excess of magnesium. A second sample of propanoic acid of mass $3.70\text{ g}$ reacts with an excess of sodium. Both reactions go to completion forming a gas.

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• Question 1May/June 2026, paper 12Multiple choice1 mark

  Which mass of aluminium is needed to produce $0.10\text{ mol}$ of ${\text{Al}}_2{\text{Cl}}_6$?

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• Question 14Oct/Nov 2025, paper 12Multiple choice1 mark

  $20.0{\text{ cm}}^3$ of hydrogen peroxide decomposes to water and oxygen in the presence of a suitable catalyst. $160{\text{ cm}}^3$ of oxygen, measured at room conditions, is produced in $5.00\text{ minutes}$.

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• Question 8Oct/Nov 2023, paper 12Multiple choice1 mark

  In an experiment, $0.100\text{ mol}$ of propan-1-ol is burnt completely in $12.0{\text{ dm}}^3$ of oxygen, measured at room conditions. What is the final volume of gas, measured at room conditions?

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• Question 2May/June 2026, paper 12Multiple choice1 mark

  Compound Q contains the elements C, H and O only. When completely combusted, $2.00\text{ g}$ of Q produces $4.00\text{ g}$ of carbon dioxide and $1.63\text{ g}$ of water. What is the empirical formula of Q?

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• Question 21Oct/Nov 2025, paper 12Multiple choice1 mark

  In an experiment, $0.600\text{ mol}$ of chlorine gas, ${\text{Cl}}_2$, is reacted with an excess of hot aqueous sodium hydroxide. One of the products is ${\text{NaClO}}_3$. Which mass of ${\text{NaClO}}_3$ is formed?

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• Question 9Oct/Nov 2023, paper 12Multiple choice1 mark

  At a temperature of $2500\text{ K}$ and a pressure of $1.00\times {10}^{-4}\text{ Pa}$, a sample of $0.321\text{ g}$ of sulfur vapour has a volume of $2.08\times {10}^6{\text{ m}}^3$. What is the molecular formula of sulfur under these conditions?

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• Question 20May/June 2026, paper 12Multiple choice1 mark

  When calcium nitrate thermally decomposes, oxygen is one of the products. Which volume of oxygen is produced at room conditions when $0.50\text{ mol}$ of calcium nitrate thermally decomposes?

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• Question 38Oct/Nov 2025, paper 12Multiple choice1 mark

  Butylamine can be produced by the reaction of butanenitrile with hydrogen in the presence of a suitable catalyst. Which volume of hydrogen, measured at room conditions, is required to react completely with $0.500\text{ g}$ of butanenitrile?

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• Question 30May/June 2026, paper 12Multiple choice1 markHas a diagram

  A sample of 1-bromopropane, ${\text{C}}_3{\text{H}}_7\text{Br}$, of mass $36.9\text{ g}$ is heated with an excess of $\text{KCN}$ in ethanol. The reaction gives a $78.0\mathrm{\%}$ yield of the desired organic product. Which row is correct?

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