Chemical Formulae, Equations and Calculations Part 2
5 marks · EasyZinc sulfate solution reacts with barium chloride solution: \[ \ce{ZnSO4(aq) + BaCl2(aq) -> BaSO4(s) + ZnCl2(aq)} \] A titration is carried out to determine the amount of barium chloride solution required to completely react with a given volume of zinc sulfate solution.
Write the mole ratio of zinc sulfate to barium chloride in the balanced chemical equation.
In a titration, 30.0 cm³ of 0.150 mol/dm³ zinc sulfate solution reacts exactly with 30.0 cm³ of barium chloride solution. Calculate the number of moles of zinc sulfate used.
Using your answers from (a) and (b), calculate the number of moles of barium chloride that react.
Calculate the concentration (in mol/dm³) of the barium chloride solution.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) 1:1
(b) 0.0045 mol
(c) 0.0045 mol
(d) 0.150 mol/dm³
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States correct 1:1 mole ratio from equation (ZnSO₄ : BaCl₂).
M1 (b) · 1 mark · Converts 30.0 cm³ to 0.0300 dm³ and uses moles = volume × concentration.
M2 (c) · 1 mark · Uses 1:1 ratio to state moles of BaCl₂ equals moles of ZnSO₄. (follow-through)
M3 (d) · 1 mark · Uses concentration = moles/volume with their value for BaCl₂ and 0.0300 dm³. (follow-through)
A1 (d) · 1 mark · Calculates 0.150 mol/dm³ for the concentration of BaCl₂. (follow-through)
Worked solution
(a) From the equation:\nZnSO₄(aq) + BaCl₂(aq) → BaSO₄(s) + ZnCl₂(aq)
Mole ratio ZnSO₄:BaCl₂ is 1:1.
(b) Moles of ZnSO₄ = volume (dm³) × concentration
(c) The ratio is 1:1, so moles of BaCl₂ = 0.0045 mol.
(d) Concentration of BaCl₂ = moles / volume (dm³):