Camp science  part 2  chemistry  july 2011
Q6.RUSTING= SM 2007 no.6 <ul><li>(i) State the conditions for the rusting of iron . </li></ul>P PRESENCE OF WATER  AND OXY...
(ii) labelled diagram the rusting of iron. Anode: Fe     Fe 2+  + 2e Cathode : O 2  + 2H 2 O + 4e     4OH - 2 O 2   drop...
(b) (i) Describe the reactions that occur after the Fe  2+  and OH -  ions are formed . <ul><li>Fe  2+  combine with OH - ...
<ul><li>State the change in the oxidation number of iron in 6(b)(i) </li></ul><ul><li>Fe(OH) 2   to iron(III)oxide  </li><...
c(i) Explain how the zinc plates protect the iron ship from rusting. <ul><li>Zinc is more electropositive  than iron </li>...
( ii) Write the half equation for the reaction in 6(c)(i).   Zn     Zn   +2   + 2e
 
SPM 2006 SECTION B ( NO 7)
(a)  The following are the formulae of two compounds. Al 2 O 3 Cu 2 O   <ul><li>(i)  Based on the two formulae, state the ...
Al 2 O 3  = 0 2Al  + 3O  =0 2Al  + 3(-2) =0 2Al  = +6 Al  =+3 Cu 2 O   = 0 2Cu  + O  =0 2Cu  -2  =0 2Cu  = -2 Cu  =+1 oxid...
<ul><li>(ii)  Name both the compounds based on the IUPAC nomenclature system. [2 marks] </li></ul>Compound IUPAC nomenclat...
<ul><li>Explain the difference between the names of the two compounds based on the IUPAC nomenclature system. </li></ul><u...
<ul><li>Copper is a transition element , so has more than one oxidation number  </li></ul><ul><li>Copper(I) oxide uses a R...
<ul><li>  (b) Diagram 7 shows the set up of the apparatus for an experiment to investigate electron transfer through a sol...
<ul><li>Name the oxidation agent in the </li></ul><ul><li>experiment. [1 mark] </li></ul><ul><li>  </li></ul>Acidified Pot...
<ul><li>(ii)  Write the half equations for the reactions that occur at the negative and positive terminals.   [5 marks] </...
Half equation at positive terminal MnO 4 -  + 8H +  + 5e -   Mn 2+  + 4H 2 O Half equation at negative terminal Fe 2+  Fe ...
<ul><li>(iii)  Based on your answer in 7(b)(ii), describe the oxidation and reduction processes in terms of the electron t...
<ul><li>At the negative terminal : </li></ul><ul><li>Each Fe 2+  donates  one electron to become Fe 3+ </li></ul><ul><li>O...
<ul><li>At the positive terminal : </li></ul><ul><li>MnO 4 -  ion accept electron and  is reduced to Mn 2+  and water </li...
<ul><li>At the positive terminal </li></ul><ul><li>The purple colour of KMnO 4  becomes lighter or colourless  </li></ul><...
<ul><li>At the negative terminal : </li></ul><ul><li>The green colour of iron(II) sulphate turns brown. </li></ul><ul><li>...
End of part 2  camp science
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revison on redox-2

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revison on redox-2

  1. 1. Camp science part 2 chemistry july 2011
  2. 2. Q6.RUSTING= SM 2007 no.6 <ul><li>(i) State the conditions for the rusting of iron . </li></ul>P PRESENCE OF WATER AND OXYGEN
  3. 3. (ii) labelled diagram the rusting of iron. Anode: Fe  Fe 2+ + 2e Cathode : O 2 + 2H 2 O + 4e  4OH - 2 O 2 drop of water A piece of iron O 2 O 2 rust 1 2 3 4 e e Fe 2+
  4. 4. (b) (i) Describe the reactions that occur after the Fe 2+ and OH - ions are formed . <ul><li>Fe 2+ combine with OH - to form iron(II)hydroxide // </li></ul><ul><li>Fe 2+ + 2 OH -  Fe(OH) 2 </li></ul><ul><li>Fe(OH) 2 is oxidised by air to form hydrated iron (III) oxide </li></ul><ul><li>Fe 2 O 3 .xH 2 O is called rust </li></ul>
  5. 5. <ul><li>State the change in the oxidation number of iron in 6(b)(i) </li></ul><ul><li>Fe(OH) 2 to iron(III)oxide </li></ul>+ 2 to +3
  6. 6. c(i) Explain how the zinc plates protect the iron ship from rusting. <ul><li>Zinc is more electropositive than iron </li></ul><ul><li>Zinc atom release electron to form ion zinc </li></ul><ul><li>So zinc protects iron from rusting </li></ul><ul><li>So iron does not rust </li></ul>
  7. 7. ( ii) Write the half equation for the reaction in 6(c)(i). Zn  Zn +2 + 2e
  8. 9. SPM 2006 SECTION B ( NO 7)
  9. 10. (a) The following are the formulae of two compounds. Al 2 O 3 Cu 2 O   <ul><li>(i) Based on the two formulae, state the oxidation number for aluminium and copper. [2 marks] </li></ul>
  10. 11. Al 2 O 3 = 0 2Al + 3O =0 2Al + 3(-2) =0 2Al = +6 Al =+3 Cu 2 O = 0 2Cu + O =0 2Cu -2 =0 2Cu = -2 Cu =+1 oxidation number of Al is +3 oxidation number of copper is +1
  11. 12. <ul><li>(ii) Name both the compounds based on the IUPAC nomenclature system. [2 marks] </li></ul>Compound IUPAC nomenclatre system Al 2 O 3 Aluminium Oxide Cu 2 O Copper(I) Oxide
  12. 13. <ul><li>Explain the difference between the names of the two compounds based on the IUPAC nomenclature system. </li></ul><ul><li>[2 marks] </li></ul>
  13. 14. <ul><li>Copper is a transition element , so has more than one oxidation number </li></ul><ul><li>Copper(I) oxide uses a Roman number </li></ul><ul><li>Aluminium has only one oxidation number ,so Aluminium does not use a Roman number </li></ul>Answer:
  14. 15. <ul><li>  (b) Diagram 7 shows the set up of the apparatus for an experiment to investigate electron transfer through a solution. </li></ul>Diagram 7
  15. 16. <ul><li>Name the oxidation agent in the </li></ul><ul><li>experiment. [1 mark] </li></ul><ul><li>  </li></ul>Acidified Potassium manganate(VII) solution Answer:
  16. 17. <ul><li>(ii) Write the half equations for the reactions that occur at the negative and positive terminals. [5 marks] </li></ul>
  17. 18. Half equation at positive terminal MnO 4 - + 8H + + 5e - Mn 2+ + 4H 2 O Half equation at negative terminal Fe 2+ Fe 3+ + e -
  18. 19. <ul><li>(iii) Based on your answer in 7(b)(ii), describe the oxidation and reduction processes in terms of the electron transfer that occurs at the negative and positive terminals. </li></ul><ul><li>State also the changes that can be observed after 10 minutes. [8 marks] </li></ul>
  19. 20. <ul><li>At the negative terminal : </li></ul><ul><li>Each Fe 2+ donates one electron to become Fe 3+ </li></ul><ul><li>Oxidation process takes place </li></ul><ul><li>The donated electron are taken up by MnO 4 - which is reduced to Mn 2+ and water </li></ul>Answer :
  20. 21. <ul><li>At the positive terminal : </li></ul><ul><li>MnO 4 - ion accept electron and is reduced to Mn 2+ and water </li></ul><ul><li>In this process, reduction has take place </li></ul>
  21. 22. <ul><li>At the positive terminal </li></ul><ul><li>The purple colour of KMnO 4 becomes lighter or colourless </li></ul><ul><li>purple MnO 4 - decrease in quantity because all of ions are changed to colourless Mn 2+ ion </li></ul>Changes after 10 minutes
  22. 23. <ul><li>At the negative terminal : </li></ul><ul><li>The green colour of iron(II) sulphate turns brown. </li></ul><ul><li>This is due to the formation of iron(III) sulphate which is brown in colour </li></ul>
  23. 24. End of part 2 camp science
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