CIE Nov 2014 v2 Paper 5 Q1

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A solder is an alloy of metals which is used to join other metal pieces together. A specialist solder that can be used to join together pieces of aluminium is made from a mixture by mass of 65% zinc, 20% aluminium and 15% copper. PMT You are to plan an experimental procedure to con rm the composition of a powdered sample of this solder, by adding reagents and then extracting from the mixture each of the following in sequence; the copper metal, (i) (ii) the aluminium as aluminium hydroxide, (iii) the zinc as zinc hydroxide. You are provided witha sample of this solder, with approximate mass 4 g,1.00 mol dm3 sulfuric acid,1.00 mol dm3 ammonia. No other reagents should be used. Standard laboratory equipment is available including a balance, accurate to two decimal places. (a) Complete theowchart below to show the order in which the reagents would be added to the solder to allow you to extract and separate the components as copper metal, (Step 1), aluminium hydroxide, (Step 2), and zinc hydroxide, (Step 3). You are reminded that aqueous ammonia contains both the base OH and the complex-forming molecule NH3. Step 1 reagent(s) added Step 2 reagent(s) added Step 3 reagent(s) addedsubstance(s) present at the end of the reaction substance(s) present at the end of the reaction substance(s) present at the end of the reaction soldersubstance(s) removed by filtration (if any) substance(s) removed by filtration (if any) substance(s) removed by filtration (if any)[5]UCLES 2014 9701/52/O/N/14<br /> PMT (b) For some of the steps in the procedure you would need to be careful to add an appropriate quantity of a reagent. For each step of your procedure explain why particular quantities of reagent should be chosen. Step 1Step 2Step 3[4] (c) The aluminium hydroxide and zinc hydroxide that have been extracted are dif cult to dry so it is better to convert them to their oxides. Describe how this could be done and how you would make sure that each hydroxide had been completely converted into its oxide.[2]UCLES 2014 9701/52/O/N/14 [Turn over<br /> PMT (d) The purpose of the experiment is to con rm the composition of the solder. When the experiment is carried out state the measurements that would be taken, what you would do to the copper to make sure that the correct value is obtained.[2] (e) If the mass of aluminium oxide obtained was 1.50 g, calculate the mass of aluminium that was present in the solder. (Ar: Al, 27.0; O, 16.0) [1] (f) Even if the experimental dif culties of extracting all of the copper from the mixture were overcome, it would be dif cult to obtain an accurate mass of copper from this experiment. Suggest why.[1] [Total: 15]UCLES 2014 9701/52/O/N/14<br /> PMT QUESTION 2 STARTS ON THE NEXT PAGE.UCLES 2014 9701/52/O/N/14 [Turn over<br />

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