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1 markMole Concept

CSEC Chemistry · January 2006 · Paper 2 · Question 1(a)(iii)

A student is provided with two solutions, X (aqueous sulphuric acid, 4.9 g dm⁻³) and Y (aqueous sodium hydroxide, 5.0 g of impure NaOH in 1 dm³). The student titrates X against 25.0 cm³ of Y to determine the purity of the sodium hydroxide. Figure 1 shows burette readings before and after each titration.

Calculate the concentration of sulphuric acid in solution X in mol dm⁻³. (Relative atomic mass: H = 1; S = 32; O = 16)

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Other parts of this question

  1. 1(a)(i)In the space below construct Table 1 to record the titration results. You should include the initial and final burette volumes and the volume of solution X…[7 marks]
  2. 1(a)(ii)What is the volume of X to be used for calculation?[1 mark]
  3. 1(a)(iv)Calculate the number of moles of sulphuric acid used in the titration.[1 mark]
  4. 1(a)(v)Write a balanced equation for the reaction between the sulphuric acid and sodium hydroxide solutions.[2 marks]
  5. 1(a)(vi)Determine the number of moles of sodium hydroxide in the 25 cm³ of solution used.[1 mark]
  6. 1(a)(vii)Calculate the concentration of NaOH in g dm⁻³. (Relative atomic mass: Na = 23; O = 16; H = 1)[2 marks]
  7. 1(a)(viii)Calculate the percentage purity of the sodium hydroxide solution.[1 mark]
  8. 1(b)(i)Draw a fully labelled diagram of the arrangement of the apparatus that the student may have used for conducting the experiment.[3 marks]
  9. 1(b)(ii)Using the graph paper on page 5, plot a graph of temperature against time.[4 marks]
  10. 1(b)(iii)From the graph determine the melting point of stearic acid.[1 mark]
  11. 1(c)(i)To a sample of solution P, dilute nitric acid is added, followed by a few drops of silver nitrate solution. Inference: No Cl⁻, Br⁻ or I⁻ ions present.[1 mark]
  12. 1(c)(ii)To a sample of solution P, a few copper turnings are added, followed by concentrated sulphuric acid. Observation: Brown fumes evolve which turn moist blue…[1 mark]
  13. 1(c)(iii)To a sample of solution P, a few drops of acidified aqueous potassium manganate (VII) solution are added. Observation: (missing) Inference: The potassium…[1 mark]
  14. 1(c)(iv)To a sample of solution P, aqueous sodium hydroxide is added, until in excess. Observation: A green precipitate forms. The precipitate is insoluble in excess…[2 marks]

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