Formulas: past paper questions

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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 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 26May/June 2026, paper 11Multiple choice1 mark

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

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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 6May/June 2025, paper 11Multiple choice1 mark

  P is a compound that burns in an excess of oxygen to give carbon dioxide and water only.

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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 25May/June 2026, paper 13Multiple choice1 markHas a diagram

  The skeletal structure of hexamine is shown. What is the empirical formula of hexamine?

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• Question 1Oct/Nov 2024, paper 21Structured16 marks

  Cobalt, rhodium and iridium are metals in the same group of the Periodic Table. The shorthand electronic configuration of cobalt is [Ar]$3{\text{d}}^{7}4{\text{s}}^2$. Identify what is meant by [Ar] by giving its full electronic configuration.

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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 15May/June 2025, paper 12Multiple choice1 markHas a diagram

  The skeletal formulae of arginine and lysine are shown. [Skeletal formulae of arginine and lysine] Which row is correct?

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• Question 1May/June 2024, paper 12Multiple choice1 mark

  Which pair of formulae is correct?

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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 39May/June 2025, paper 13Multiple choice1 mark

  An organic compound, T, contains only one functional group. Compound T has the empirical formula ${\text{C}}_2{\text{H}}_4\text{O}$. Some functional groups are listed.

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• Question 3May/June 2024, paper 12Multiple choice1 markHas a diagram

  The first eight successive ionisation energies for two elements of Period 3 of the Periodic Table are shown in the graphs. What is the formula of the ionic compound formed from these elements?

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• Question 4May/June 2025, paper 21Structured9 marksHas a diagram

  The structure of vitamin C is shown in Fig. 4.1. Deduce the empirical formula of vitamin C.

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• Question 3May/June 2024, paper 23Structured7 marks

  Write an equation to show the reaction for the standard enthalpy change of formation of ${\mathrm{H}}_2\mathrm{O}$.

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• Question 5May/June 2025, paper 22Structured5 marksHas a diagram

  The structure of vitamin C is shown in Fig. 5.1. Fig. 5.1 Deduce the empirical formula of vitamin C.

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• Question 33May/June 2023, paper 13Multiple choice1 mark

  T is an organic compound which contains 66.7% by mass of carbon. T also contains one atom of oxygen per molecule. T reacts with alkaline ${\mathrm{I}}_2(\mathrm{a}\mathrm{q})$ to produce a yellow precipitate.

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• Question 36May/June 2023, paper 13Multiple choice1 mark

  Compound Q can be hydrolysed by $\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})$. The two products of this hydrolysis have the same empirical formula. What could Q be?

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