62 Results 63 1 2 3 4 5 Q1 An experiment was carried out to measure the emf of

62 results 63 1 2 3 4 5 q1 an experiment was carried

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Results: 63 1 2 3 4 5
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Q1. An experiment was carried out to measure the e.m.f. of this cell. Al(s) Al 3+ (aq) H + (aq) H 2 (g) Pt(s) (a) The aluminium used as the electrode is rubbed with sandpaper prior to use. Suggest the reason for this. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (1) (b) Draw a labelled diagram of a suitable apparatus for the right-hand electrode in this cell. You do not need to include the salt bridge or the external electrical circuit. (2) (c) A simple salt bridge can be prepared by dipping a piece of filter paper into potassium carbonate solution. Explain why such a salt bridge would not be suitable for use in this cell. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2) (Total 5 marks) 64
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Q2. This table shows some standard electrode potential data. Electrode half-equation E ϴ / V Au + (aq) + e Au(s) +1.68 O 2 (g) + 2H + (aq) + 2e H 2 O(l) +1.23 Ag + (aq) + e Ag(s) +0.80 Fe 3+ (aq) + e Fe 2+ (aq) +0.77 Cu 2+ (aq) + 2e Cu(s) +0.34 Fe 2+ (aq) + 2e Fe(s) −0.44 (a) Draw a labelled diagram of the apparatus that could be connected to a standard hydrogen electrode in order to measure the standard electrode potential of the Fe 3+ / Fe 2+ electrode. In your diagram, show how this electrode is connected to the standard hydrogen electrode and to a voltmeter. Do not draw the standard hydrogen electrode. State the conditions under which this cell should be operated in order to measure the standard electrode potential. Conditions ..................................................................................................... ........................................................................................................................ ........................................................................................................................ (5) 65
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(b) Use data from the table to deduce the equation for the overall cell reaction of a cell that has an e.m.f. of 0.78 V. Give the conventional cell representation for this cell. Identify the positive electrode. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (4) (c) Use data from the table to explain why Au + ions are not normally found in aqueous solution. Write an equation to show how Au + ions would react with water. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (3) (d) Use data from the table to predict and explain the redox reactions that occur when iron powder is added to an excess of aqueous silver nitrate. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (3) (Total 15 marks) 66
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WORK SHEET 9 To investigate how pH changes when a weak acid reacts with a strong base Whenever possible, students should work individually. If it is essential to work in a pair or in a small group, because of the availability of apparatus, supervisors must be satisfied that they are able to assess the contribution from each student to the practical activity. Requirements two 50 cm 3 burettes two funnels 100 cm 3 beaker deionised (or distilled) water in a wash bottle stand and clamp pH meter/probe 0.100 mol dm –3 sodium hydroxide solution 0.100 mol dm –3 ethanoic acid solution standard pH buffer solutions at pH 4.00, 7.00 and 9.20 stirring rod graph paper. Centres may choose to use other weak acid/strong base combinations or strong acid/weak base combinations. Suggested method The aim of this experiment is to investigate how pH changes when a weak acid reacts with a strong base. Introduction This experiment investigates how the pH of a solution of ethanoic acid changes as sodium hydroxide solution is added.
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  • Fall '19
  • Rupalben Yogesh Patel
  • Enthalpy, pH

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