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2 marksOxidation – Reduction Reactions

CSEC Chemistry · May/June 2011 · Paper 2 · Question 6(c)(iii)

Vitamin C content in orange juice is determined by titration with iodine solution using starch indicator. Vitamin C reacts with iodine to form iodide ions; excess iodine reacts with starch. A sample of orange juice was divided into two equal portions, A and B. Sample B was boiled and cooled. Both samples were titrated against iodine solution.

With reference to the oxidation number of iodine, explain whether vitamin C is acting as an oxidizing or a reducing agent when it reacts with iodine.

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Other parts of this question

  1. 6(a)Suggest a reason for this.[2 marks]
  2. 6(b)(i)Explain how natural OR commercial tenderizers work when used to tenderize meat.[3 marks]
  3. 6(b)(ii)List ONE advantage and ONE disadvantage of using commercial tenderizers over natural tenderizers.[2 marks]
  4. 6(b)(iii)Baking soda, NaHCO₃, can also be used to tenderize meat. Suggest why this is possible.[2 marks]
  5. 6(c)(i)What colour change would you expect at the end point in BOTH cases?[1 mark]
  6. 6(c)(ii)Which sample, A or B, would require the LARGER volume of iodine? Explain your answer.[3 marks]

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