Question

e (Descioe the working prncipie of a vacuum phototube, (ii) Justify whether it can be used in this instrument. 4. Direct potentiometric analysis requires the use of a pair of electrodes and a voltmeter (a) (i) Write down the reductive half reaction occurs on a silver-silver chloride electrode. (i) Justify whether this electrode can serve as a reference electrode in this method. (b) There is usually a salt bridge at the end of the reference electrode (i) What is the major function of this salt bridge? (i) Suggest and justify a kind of appropriate electrolyte to be used in this salt bridge. (C) (i) Justify whether there will be random or systematic eror if the liquid-junction potentials developed in the salt bridge are different in standard and testing solutions. (i) Propose a practical way how we can make the liquid-junction potentials in standard and testing solutions as close as possible. (d) Show whether a piece of silver wire is suitable to serve as an indicator electrode in this method for determining (i) silver ions (Ag), and (i) chloride (Cr). (e) (i) Justify whether we should stir the solution during direct potentiometric measurements (i) Why is a voltmeter with a very large internal resistance needed?

Answer 1

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