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# Redox= quiz part 2 with answers

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### Redox= quiz part 2 with answers

1. 19. Why does the surface of the iron in the middle of water droplet serves as the anode? <ul><li>Anode is area where electron is </li></ul><ul><li>……………………………… </li></ul><ul><li>Atom ……………………here ……………………………electron to form </li></ul><ul><li>………………………… .. </li></ul>
2. 20. <ul><li>Fe  Fe 2+ + 2e </li></ul>Write half equation for the reaction at (i) above
3. 21. The electrons released by the iron flows to the edge of the water where there is plenty of dissolved oxygen. Why does the iron surface here serve as the cathode? <ul><li>Cathode is area where electron is </li></ul><ul><li>……………………………… </li></ul><ul><li>…………………………… ..…and ………………………. </li></ul><ul><li>here …………….. electron to </li></ul><ul><li>form ……………………… </li></ul>
4. 22. <ul><li>2H 2 O + 4e + O 2  4OH - </li></ul>Write half equation for the reaction at (iii) above
5. 23. <ul><li>2H 2 O + 4e + O 2  4OH - </li></ul>The iron(II) ions formed in (i) combined with the hydroxide ions formed in (iii) to form iron(II) hydroxide. Write the equation for the reaction here <ul><li>Fe  Fe 2+ + 2e </li></ul>Fe 2+ +2OH -  Fe(OH) 2
6. 24. <ul><li>Fe 2 O 3 .xH 2 O </li></ul>The iron(II) hydroxide is rapidly oxidized by air to form rust. Write formula of rust
7. 25. Draw simple diagram of mechanism of rusting
8. 26. Method of metals extraction <ul><li>Aluminium=electrolysis of molten aluminium oxide </li></ul><ul><li>Iron= heat iron oxide with carbon </li></ul><ul><li>Copper= heat copper(II) sulphide strongly in air </li></ul><ul><li>Gold= unreactive metal= obtained free </li></ul>
9. 27. What kind of metals A) prevent rusting and B) encourage rusting <ul><li>A) metals above iron in ECS </li></ul><ul><li>B) metals below iron in ECS </li></ul>
10. 28. ECS and RS <ul><li>K </li></ul><ul><li>Na </li></ul><ul><li>Ca </li></ul><ul><li>Mg </li></ul><ul><li>Al </li></ul><ul><li>Zn </li></ul><ul><li>Fe </li></ul><ul><li>Sn </li></ul><ul><li>Pb </li></ul><ul><li>Cu </li></ul><ul><li>Hg </li></ul><ul><li>Ag </li></ul><ul><li>Au </li></ul>(RS) C (RS) H H (ECS)
11. 29. Differences between electrolytic cell and voltaic/chemical cell <ul><li>Electrolytic cell </li></ul><ul><li>Oxidation occur at positive electrode </li></ul><ul><li>because negative ions </li></ul><ul><li>released electrons here </li></ul><ul><li>Chemical cell cell </li></ul><ul><li>Oxidation occur at negative electrode </li></ul><ul><li>because metal atom </li></ul><ul><li>release electrons here </li></ul>
12. 30. Differences between electrolytic cell and voltaic/chemical cell <ul><li>Electrolytic cell </li></ul><ul><li>Reduction occur at negative electrode </li></ul><ul><li>because positive ions </li></ul><ul><li>gain electrons here </li></ul><ul><li>Chemical cell cell </li></ul><ul><li>Reduction occur at positive electrode </li></ul><ul><li>because positive ions </li></ul><ul><li>gain electrons here </li></ul>