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2 marksRates of Reaction

CSEC Chemistry · May/June 2005 · Paper 2 · Question 1(a)(iv)

A student investigates the effect of temperature on the rate of reaction between aqueous sodium thiosulphate and hydrochloric acid, which produces sulfur, sulfur dioxide, sodium chloride, and water. The rate is monitored by measuring the time for a fixed amount of sulfur precipitate to form. Figure 1 shows stopwatch times and corresponding thermometer readings for experiments where reactant concentrations are constant.

From the graph, determine the time expected to be taken for the appearance of the sulphur precipitate if the reaction were carried out at 50°C. Indicate on your graph how you arrived at your answer.

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Other parts of this question

  1. 1(a)(i)In the space below, construct a suitable table and record on it, the temperatures at which the reaction took place with the corresponding times in seconds for…[4 marks]
  2. 1(a)(ii)Using the graph paper provided on page 5, plot a graph of temperature versus time in seconds.[3 marks]
  3. 1(a)(iii)What conclusion can be drawn about the rate of the reaction from the graph?[1 mark]
  4. 1(a)(v)From the information given on page 3 in the introduction to this question, write a balanced chemical equation for the reaction between aqueous sodium…[2 marks]
  5. 1(b)(i)Heat a small portion of solid Y in a test tube, gently at first and then strongly. Observations: colourless gas evolved with a choking odour; turns acidified…[10 marks]
  6. 1(b)(ii)To the remaining portion of solid Y, add 20 cm³ of distilled water, stir to dissolve and filter. Collect the filtrate and divide into three (3) equal portions.…[10 marks]
  7. 1(b)(iii)To the first portion of the filtrate from (b) above, add aqueous sodium hydroxide slowly until in excess. Observations: a green precipitate is formed;…[10 marks]
  8. 1(b)(iv)To the second portion of the filtrate from (b) above, add aqueous silver nitrate followed by aqueous ammonia. Observations: white precipitate is formed;…[10 marks]
  9. 1(b)(v)To the third portion of the filtrate from (b) above, add aqueous barium nitrate followed by aqueous nitric acid. Observations: a white precipitate is formed;…[10 marks]
  10. 1(c)(i)Hypothesis to be tested[8 marks]
  11. 1(c)(ii)Materials and apparatus[8 marks]
  12. 1(c)(iii)Method[8 marks]
  13. 1(c)(iv)Variables controlled[8 marks]
  14. 1(c)(v)Data to be collected[8 marks]
  15. 1(c)(vi)Results linked to hypothesis[8 marks]

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