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CSEC Chemistry · January 2015 · Paper 2 · Question 1(a)(i)

The solubility of solid X in water at various temperatures is determined through a series of experiments (1-5). The procedure involves adding 2g of X to varying volumes of water, heating until dissolved, then cooling and noting the temperature at which crystals of X first reappear. Some data is in Table 1, and reappearance temperatures for experiments 2-5 are shown in Figure 1.

recording the temperatures at which the crystals of X reappear in EACH experiment using the information in Figure 1

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  1. 1(a)(ii)determining and recording the corresponding values for the solubility of X. [At each temperature, Solubility of X = (mass of X / mass of water) × 100; assume 1…[3 marks]
  2. 1(b)Using the axes on the grid provided on page 5, plot a graph of solubility of X (g/100 g water) against temperature in °C. Draw a best-fit curve through the…[4 marks]
  3. 1(c)What deduction about the solubility of X can be made from the graph drawn in 1 (b) above?[1 mark]
  4. 1(d)Using the equation given in 1 (a) (ii) and the graph drawn in 1 (b), calculate the minimum volume of water which is required to dissolve 2 g of X at 60 °C.[3 marks]
  5. 1(e)Distinguish between 'a solution' and 'a suspension'.[2 marks]
  6. 1(f)Besides temperature, state TWO other factors that affect the rate at which a solute dissolves.[2 marks]
  7. 1(g)Complete Table 2 to show the observations and inferences from tests carried out on a solution, M.[1 mark]

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