CIE Nov 2014 v3 Paper 5 Q2

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PMT An aqueous solution of nickel(II) sulfate, NiSO4, has a concentration of exactly 0.500 mol dm3. In an experiment, 100.0 cm3 of this solution was accurately measured into a beaker and 0.0200 mol of solid potassium iodate(V), KIO3, was added to it. After stirring, a saturated solution of nickel(II) iodate was formed together with a precipitate of nickel(II) iodate. The precipitate wasltered off, dried and weighed. The mass of precipitate obtained was recorded in the table below. The experiment was repeated six more times using 100.0 cm3 of aqueous nickel(II) sulfate each time but adding increasing amounts of solid potassium iodate(V). The results obtained from these experiments were also recorded in the table below. experiment number amount of potassium iodate(V) added / mol mass of precipitate formed / g 1 2 3 4 5 6 7 0.0200 0.0300 0.0400 0.0500 0.0600 0.0700 0.0800 3.87 6.71 7.92 8.80 11.97 13.95 15.92 The concentration of ions in a saturated solution of a slightly soluble salt can be expressed using a solubility product. For nickel(II) iodate this is de ned as: solubility product = [Ni2+(aq)][IO3 (aq)]2 (a) (i) Write an ionic equation for the reaction that has taken place. Include state symbols.[1] (ii) Use the equation in (i) to deduce the amount in mol of potassium iodate(V) that would react with the nickel(II) sulfate solution in this experiment. (iii) If, after the amount in (ii) had been added further potassium iodate(V) was added, state what effect, if any, this would have on the mass of precipitate obtained.[1] [1]UCLES 2014 9701/53/O/N/14<br /> (b) (i) Plot points on the grid below to show the amount in mol of potassium iodate(V) added against the mass of precipitate formed. Draw a line of bestt. PMT 22.0 20.0 18.0 16.0 14.0 12.0 10.0 8.0 6.0 4.0 2.0 mass of precipitate formed / g 0.0 0.00 0.02 0.04 0.06 0.08 0.10 0.12 potassium iodate(V) added / molUCLES 2014 9701/53/O/N/14 [2] [Turn over<br /> PMT (ii) Circle any anomalous point(s) on your graph. [1] (iii) Suggest which part of the experimental procedure would make it dif cult to achieve accurate results.[1] (iv) Add points on your graph to indicate the approximate mass of precipitate that would be obtained if each of the following amounts in mol of potassium iodate(V) were added.0.1000 mol0.1200 mol [2] (c) (i) In this reaction some of the nickel(II) iodate has been precipitated but some remains dissolved. Calculate the total mass of nickel(II) iodate (both precipitated and dissolved) formed in experiment 3 when all of the added potassium iodate(V) ions have fully reacted with nickel(II) sulfate. The relative formula mass of nickel(II) iodate is 408.7. [1]UCLES 2014 9701/53/O/N/14<br /> (ii) Use your answer to (i) and the mass of precipitate of nickel(II) iodate in experiment 3 to calculate the mass of nickel(II) iodate dissolved in solution. PMT Calculate the amount in moles of nickel(II) iodate in solution. Calculate the amount in moles of iodate(V) ions that remain in the 100.0 cm3 of solution. [3]UCLES 2014 9701/53/O/N/14 [Turn over<br /> (iii) The solubility product of nickel(II) iodate = [Ni2+(aq)][IO3 (aq)]2. 10 In experiment 3, the amount in moles of Ni2+(aq) that remain in the 100.0 cm3 of solution is 0.0306. Use this, and yournal answer in (ii), to calculate the solubility product. PMT [2] [Total: 15]UCLES 2014 9701/53/O/N/14<br />

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