IGCSE Chemistry Stoichiometry topical questions

This question is about formulae and equations.

1. (a)Write the formula of carbon dioxide.[1]
2. (b)State the total number of atoms in one molecule of methane, CH₄.[1]
3. (c)State what is meant by the molecular formula of a compound.[1]

Calculate the relative molecular mass of sulfuric acid, H₂SO₄. (Aᵣ: H = 1, S = 32, O = 16)

Magnesium burns in bright white light: magnesium + oxygen → magnesium oxide.

1. (a)Name the reactants in this reaction.[1]
2. (b)Complete the balanced symbol equation by filling the gaps: __Mg + O₂ → __MgO[2]
3. (c)Write the state symbol that should follow O₂ in this reaction.[1]

This question is about relative masses of atoms.

1. (a)Define the relative atomic mass, Aᵣ, of an element.[2]
2. (b)Explain why the relative atomic mass of chlorine is 35.5 rather than a whole number.[2]

This question uses the mole.

1. (a)Calculate the mass of 0.20 mol of sodium hydroxide, NaOH. (Aᵣ: Na = 23, O = 16, H = 1)[2]
2. (b)Calculate the volume occupied by 0.20 mol of carbon dioxide at room temperature and pressure. (molar gas volume = 24 dm³)[2]

A gas cylinder contains 14.6 g of butane, C₄H₁₀. (Aᵣ: C = 12, H = 1; Avogadro constant = 6.02 × 10²³)

1. (a)Calculate the relative molecular mass of butane.[1]
2. (b)Calculate the amount, in moles, of butane in the cylinder.[2]
3. (c)Calculate the number of butane molecules in the cylinder.[1]

Hydrogen burns in excess oxygen: 2H₂(g) + O₂(g) → 2H₂O(l). A student burns 0.40 mol of hydrogen completely.

1. (a)Deduce the amount, in moles, of water formed.[1]
2. (b)Calculate the mass of water formed. (Mᵣ = 18)[1]
3. (c)Calculate the volume of oxygen used at room temperature and pressure. (molar gas volume = 24 dm³)[2]

A compound contains 40.0% carbon, 6.7% hydrogen and 53.3% oxygen by mass. Its relative molecular mass is 60. (Aᵣ: C = 12, H = 1, O = 16)

1. (a)Calculate the empirical formula of the compound.[3]
2. (b)Deduce the molecular formula of the compound.[2]

25.0 g of calcium carbonate is heated strongly and decomposes: CaCO₃ → CaO + CO₂. (Aᵣ: Ca = 40, C = 12, O = 16)

1. (a)Calculate the mass of calcium oxide that the equation predicts should be formed.[2]
2. (b)In the experiment only 12.0 g of calcium oxide is obtained. Calculate the percentage yield.[2]

1.2 g of magnesium ribbon is added to 50 cm³ of 1.0 mol/dm³ dilute hydrochloric acid: Mg + 2HCl → MgCl₂ + H₂. (Aᵣ: Mg = 24; molar gas volume = 24 dm³)

1. (a)Calculate the amount, in moles, of magnesium used.[1]
2. (b)Calculate the amount, in moles, of hydrochloric acid used.[1]
3. (c)Identify the limiting reagent and explain your choice.[1]
4. (d)Calculate the volume of hydrogen gas produced at room temperature and pressure.[2]