Balanced equations and reacting massesEdexcel A-Level Chemistry: Subtopic test

1. 1
   A student reacts 2.50 g of marble chips (calcium carbonate) with excess dilute hydrochloric acid in a conical flask.

   (a)

   Which is the correct balanced equation, with state symbols, for the reaction?

   [1 mark]

   • ACaCO₃(s) + HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l)
   • BCaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l)
   • CCaCO₃(s) + 2HCl(aq) → CaCl₂(s) + CO₂(g) + H₂O(l)
   • DCaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(aq) + H₂O(g)

   (b)

   Which is the correct ionic equation for the reaction, with spectator ions removed?

   [1 mark]

   • ACaCO₃(s) + 2H⁺(aq) → Ca²⁺(aq) + CO₂(g) + H₂O(l)
   • BCO₃²⁻(aq) + 2H⁺(aq) → CO₂(g) + H₂O(l)
   • CCaCO₃(s) + 2H⁺(aq) + 2Cl⁻(aq) → Ca²⁺(aq) + 2Cl⁻(aq) + CO₂(g) + H₂O(l)
   • DCa²⁺(aq) + 2Cl⁻(aq) → CaCl₂(aq)

   (c)

   Calculate the volume of carbon dioxide produced at room temperature and pressure. M(CaCO₃) = 100.1 g mol⁻¹ and the molar volume of a gas is 24.0 dm³ mol⁻¹.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student mixes 20.0 cm³ of 0.150 mol dm⁻³ aqueous lead(II) nitrate with excess aqueous potassium iodide. A precipitate forms.

   (a)

   Which row gives the observation and the correct ionic equation, with state symbols, for the reaction?

   [1 mark]

   • AA white precipitate forms: Pb²⁺(aq) + 2I⁻(aq) → PbI₂(s)
   • BA yellow precipitate forms: Pb(NO₃)₂(aq) + 2KI(aq) → PbI₂(s) + 2KNO₃(aq)
   • CA yellow precipitate forms: Pb²⁺(aq) + 2I⁻(aq) → PbI₂(s)
   • DA yellow precipitate forms: Pb²⁺(aq) + I₂²⁻(aq) → PbI₂(s)

   (b)

   Which ions are spectator ions in this reaction?

   [1 mark]

   • APb²⁺ and I⁻
   • BPb²⁺ and NO₃⁻
   • CI⁻ and K⁺
   • DK⁺ and NO₃⁻

   (c)

   Calculate the maximum mass of lead(II) iodide formed. M(PbI₂) = 461.0 g mol⁻¹.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student adds 1.20 g of magnesium ribbon to 50.0 cm³ of 0.500 mol dm⁻³ aqueous copper(II) sulfate and stirs. The mixture warms up.

   (a)

   Write an ionic equation, with state symbols, for the reaction and explain the observations in terms of this equation.

   [3 marks]

   (b)

   Show by calculation that magnesium is in excess, and calculate the mass of copper formed. A(Mg) = 24.3 and A(Cu) = 63.5.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A small chemical works makes sodium carbonate solution and quicklime (calcium oxide). Quality-control chemists test the products and check how much gas the processes give off.

   (a)

   A 25.0 cm³ sample of 0.400 mol dm⁻³ sodium carbonate solution is added to excess dilute hydrochloric acid. Write the balanced equation with state symbols and the ionic equation, and calculate the volume of carbon dioxide produced at room temperature and pressure (molar volume 24.0 dm³ mol⁻¹) and the minimum volume of 2.00 mol dm⁻³ hydrochloric acid needed to react with all the carbonate.

   [6 marks]

   (b)

   A 500 g sample of limestone containing 92.0% calcium carbonate by mass is heated until all the calcium carbonate has decomposed to calcium oxide and carbon dioxide. Write the balanced equation with state symbols and calculate the mass of calcium oxide and the volume of carbon dioxide at room temperature and pressure produced. M(CaCO₃) = 100.1 g mol⁻¹, M(CaO) = 56.1 g mol⁻¹, molar volume = 24.0 dm³ mol⁻¹.

   [6 marks]

   Total for question 4: 12 marks

End of questions