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4 marksTitrimetric (Volumetric) Methods of Analysis

CAPE Chemistry Unit 2 · 2017 · Paper 2 · Question 5(b)

An unknown acid H2A is standardized by adding 5 cm3 portions of it to 25 cm3 of 0.25 mol dm-3 sodium hydrogen carbonate solution, recording the temperature after each addition. Figure 2 shows the temperature versus volume of acid added.

Explain fully the shape of the graph in Figure 2.

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Other parts of this question

  1. 5(a)(i)List THREE characteristics of a primary standard.[3 marks]
  2. 5(a)(ii)State whether sodium hydroxide can be considered a primary standard and give a reason for your answer.[2 marks]
  3. 5(c)(i)Calculate the number of moles of sodium hydrogen carbonate used.[1 mark]
  4. 5(c)(ii)Calculate the number of moles of acid reacted, using the equivalence point from Figure 2.[2 marks]
  5. 5(c)(iii)Calculate the concentration of the acid.[1 mark]
  6. 5(d)State ONE other titrimetric method that could be used without an indicator by the student in (b).[1 mark]
  7. 5(e)Identify the responding variable involved in the method stated in (d).[1 mark]

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