ElemTM181008

Test ID = 66

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1. (110563258) What conditions must be used when comparing one half-cell's standard electrode potential against another?
REF: 49



2. (110563232) Can manganese exist as stable Mn2+(aq) ions?
    (A) Yes
    (B) No
REF: 47



3. (110563233) Can Mn exist as stable Mn7+(aq) ions?
    (A) Yes
    (B) No
REF: 47



4. (110563243) Are there always 2 reactions in an electrochemical cell?
    (A) No
    (B) Yes
REF: 48 OCRA



5. (110563244) What are the reactions in an electrochemical cell (tick all that apply, get one wrong then 0 points)?
    (A) oxidation
    (B) reduction
    (C) disproportionation
    (D) ion-bridge transfer
    (E) redox reaction
REF: 48



6. (110563237) What is the oxidation number of the following compounds? V in V2O5; Cr in CrO42-; Cr in Cr2O72-.
REF: 47



7. (110563238) Acidified manganate (VII) ions will react with aqueous iodide ions to form iodine. First write the two half equations for the changes that occur.
REF: 47



8. (110563239) a) Write the balanced equation to show the reaction taking place.
REF: 47



9. (110563240) Use oxidation numbers to explain the redox processes which have occurred.
REF: 47



10. (110563241) Suggest why a fairly reactive metal such as zinc will not react with aqueous iodide ions in a similar manner to manganate (VII) ions.
REF: 47



11. (110563234) Are MnO4- ions good oxidising agents? What is need in order for manganate (VII) ions to work as an oxidising agent? Why?
REF: 47



12. (110563242) Draw a representation of the zinc/copper electrochemical cell and explain what is happening.
REF: 48



13. (110563245) Electrons flow through the circuit from the least reactive metal to the most reactive metal?
    (A) True
    (B) False
REF: 48



14. (110563261) List the three standard conditions used when measuring standard electrode potentials.
REF: 49



15. (110563248) Can you have such a thing as half cells involving solutions of two aqueous ions of the same element? Explain using an example.
REF: 48



16. (110563262) An electrochemical cell containing a zinc half-cell and a silver half-cell was set up using a potassium nitrate salt bridge, The cell potential at 25oC was measured to be 1.40V. Zn2+ + 2e- Zn, E = -0.76V; Ag+ + e- Ag, E= +0.80V (a) Draw a labelled diagram of this half cell.
REF: 49



17. (110563263) (b) Use the standard electrode potentials given to calculate the standard cell potential for a zinc-silver cell.
REF: 49



18. (110563264) (c) Suggest two possible reasons why the actual cell potential was different from the value calculated in part (b).
REF: 49



19. (110563265) (d) Write an equation for the overall cell reation.
REF: 49



20. (110563266) (e) Which half-cell released the electrons into the circuit? Why is this?
REF: 49



21. (110563230) List the two half equations for the reaction between zinc metal and silver nitrate (Hint: list the most eletrnegative equation first). Combine the two equations to give a balanced summary of the reation.
REF: 47



22. (110563231) What oxidation state does manganese in manganate (VII) ions go to when it is reduced?
REF: 47



23. (110563260) Fe3+ + e- Fe2+, E = +0.77V (Note arrows should be drawn as reversible but not in char set yet) Mn3+ + e- Mn2+, E=+1.48V Calculate the cell potential for the above system.
REF: 49



24. (110563235) Acidified manganate (VII) ions can be reduced by Fe2+ ions. First give the half equations and then combine them.
REF: 47



25. (110563236) What is the oxidation number of Ti in TiCl4 ?
    (A) +3
    (B) +6
    (C) +4
REF: 47



26. (110563257) Instead of the hydrogen electrode (which is a but dangerous) which type of electrode is used as a standard reference electrode instead? What is this calibrated against?
REF: 49



27. (110563246) What does a voltmeter show in the external circuit?
REF: 48



28. (110563247) What does the reading on the voltmeter represent (tick all that apply)?
    (A) ampage
    (B) cell potential
    (C) electron density
    (D) emf, Ecell
REF: 48 -EDEX



29. (110563250) Will the cell potential always be a positive value? Explain
    (A) Yes
    (B) No
REF: 48



30. (110563251) Does the metal that gets oxidised go on the left or the right in an electrochemical cell? Does this meant that this metal is an oxidising agent or reducing agent?
REF: 48



31. (110563249) When drawing an electrochemical cell by convention, which cell would you draw on the left - the one with the most negative electrode potential or the one with the most positive electrode potential? What is the equation that you then use to work out cell potential?
REF: 48



32. (110563254) Is the standard hydrogen electrode always shown on the left or the right?
    (A) Left
    (B) Right
REF: 49



33. (110563255) Since the whole cell potential = Erhs - Elhs what will the whole reading be equal to?
    (A) Erhs
    (B) Erhs
REF: 49



34. (110563256) Will the reading be positive or negative? (tick all that apply)
    (A) Positived
    (B) Negative
    (C) Both



35. (110563252) What is the coinvention for writing half equations - does the material getting oxidised get placed don the top or the bottom? Which way do the curly arrows go to denote electron flow, and hence direction of reaction?
REF: 48



36. (110563253) Define the standard electrode potential of a half cell.
REF: 49



37. (110563259) Draw a diagram of the half-cell used for determining the standard electrode potneital for the Fe3+/Fe2+ system.
REF: 49






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