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3 marksTitrimetric (Volumetric) Methods of Analysis

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

This module covers analytical methods and separation techniques. Potassium manganate (VII) solution is standardized by titration against ethanedioic acid (a primary standard) and then used to determine the percentage of Fe²⁺ in Compound R.

List THREE characteristics of ethanedioic acid that make it a suitable primary standard.

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  1. 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]
  2. 2(c)(i)Calculate EACH of the following. The number of moles MnO₄⁻ used[1 mark]
  3. 2(c)(ii)The number of moles Fe²⁺ in the 25.0 cm³ of aqueous R (aq)[1 mark]
  4. 2(c)(iii)The number of moles Fe²⁺ in 1.0 dm³ of R (aq)[1 mark]
  5. 2(c)(iv)The mass of Fe²⁺ in 1 dm³ of R (aq)[1 mark]
  6. 2(c)(v)The percentage Fe²⁺ in the compound [The mass concentration of R is 40.90 g dm⁻³][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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