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1 markTitrimetric (Volumetric) Methods of Analysis

CAPE Chemistry Unit 2 · May/June 2023 · Paper 2 · Question 2(c)(v)

25.0 cm³ of an aqueous solution of R requires 24.80 cm³ of 0.02 mol dm⁻³ manganate (VII) for complete reaction. The equation for the reaction is 5Fe²⁺ (aq) + MnO₄⁻ (aq) + 8H⁺ → 5Fe³⁺ (aq) + Mn²⁺ (aq) + 4H₂O (l).

The percentage Fe²⁺ in the compound [The mass concentration of R is 40.90 g dm⁻³]

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  1. 2(a)List THREE characteristics of ethanedioic acid that make it a suitable primary standard.[3 marks]
  2. 2(b)In preparing the solution of ethanedioic acid for titration against the manganate (VII) solution, two pieces of laboratory apparatus with a high degree of…[2 marks]
  3. 2(c)(i)Calculate EACH of the following. The number of moles MnO₄⁻ used[1 mark]
  4. 2(c)(ii)The number of moles Fe²⁺ in the 25.0 cm³ of aqueous R (aq)[1 mark]
  5. 2(c)(iii)The number of moles Fe²⁺ in 1.0 dm³ of R (aq)[1 mark]
  6. 2(c)(iv)The mass of Fe²⁺ in 1 dm³ of R (aq)[1 mark]
  7. 2(d)(i)State the meaning of the term 'retention time' (tᵣ), as applied to gas liquid chromatography (GLC).[1 mark]
  8. 2(d)(ii)Distinguish between a 'stationary phase' and a 'mobile phase' as used in chromatography.[2 marks]
  9. 2(d)(iii)Give ONE example of a stationary phase commonly used in GLC.[1 mark]
  10. 2(d)(iv)Give ONE example of the use of chromatographic methods of separation in industry.[1 mark]
  11. 2(e)(i)Define the term 'retention factor' (Rᶠ).[2 marks]
  12. 2(e)(ii)Calculate the Rᶠ value for the red dye in EACH of the two samples.[2 marks]
  13. 2(e)(iii)Deduce whether the same red dye is used to make both types of ink. Give a reason for your answer.[2 marks]
  14. 2(f)(i)Explain the term 'solvent extraction'.[2 marks]
  15. 2(f)(ii)State ONE use of solvent extraction.[1 mark]
  16. 2(f)(iii)Describe what is meant by the term 'partition coefficient' as it relates to solvent extraction.[2 marks]
  17. 2(f)(iv)Determine the mass of Q that will be extracted from 200 cm³ of aqueous solution containing 8 g of Q by shaking it with 50 cm³ of methylbenzene.[4 marks]

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