OCR A Specimen Paper 1 Q21

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24 Table 21.1 below gives the standard electrode potentials for seven redox systems. You need to use this information to answer the questions below. Redox system Equation (a) (i) Outline an experimental setup that could be used in the laboratory to measure the standard cell potential of an electrochemical cell based on redox systems 4 and 5. In your answer you should include details of the apparatus, solutions and the standard conditions required to measure this standard cell potential. 21 Eo/V +1.51 +1.33 +1.09 +0.80 +0.77 0.76 2.33 Mn2+(aq) + 4H2O(l) 2Cr3+(aq) + 7H2O(l) 2Br(aq) Ag(s) Fe2+(aq) (aq) +8H+(aq) + 5e MnO4 2(aq) +14H+(aq) + 6e Cr2O7 Br2(aq) + 2e Ag+(aq) + e Fe3+(aq) + e Zn2+(aq) + 2e Ce3+(aq) + 3e Zn(s) Ce(s) Table 21.1 Specimen[4]OCR 2014 H432/01<br /> [2] [1] [2] 25 (ii) An electrochemical cell can be made based on redox systems 2 and 4. The standard cell potential is +0.53 V. State and explain the effect on the cell potential of this cell if the concentration of silver ions is increased.(b) From Table 21.1, predict the oxidising agent(s) that will not oxidise Fe2+(aq) to Fe3+(aq).(c) An aqueous solution of iron(II) bromide is mixed with an excess of acidified solution containing manganate(VII) ions. Using Table 21.1, give the formulae of the products of any reactions that take place. . .SpecimenOCR 2014 H432/01 Turn over<br />

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