redox= quiz part 2 with answers

Why does the surface of the iron in the middle of water droplet serves as the anode?

• Anode is area where electron is ………………………………• Atom ……………………here ……………………………

electron to form

…………………………..

• Fe Fe 2+ + 2e

Write half equation for the reaction at (i) above

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?• Cathode is area where electron is ………………………………• ……………………………..…and ………………………. here …………….. electron to

form ………………………

• 2H2O + 4e + O2 4OH-

Write half equation for the reaction at (iii) above

• 2H2O + 4e + O2 4OH-

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• Fe Fe 2+ + 2e

Fe 2+ +2OH- Fe(OH)2

• Fe2O3.xH2O

The iron(II) hydroxide is rapidly oxidized by air to form rust. Write

formula of rust

Draw simple diagram of mechanism of rusting

Method of metals extraction• Aluminium=electrolysis of molten

aluminium oxide

• Iron= heat iron oxide with carbon

• Copper= heat copper(II) sulphide strongly in air

• Gold= unreactive metal= obtained free

What kind of metals A) prevent rusting and B) encourage rusting

• A) metals above iron in ECS

• B) metals below iron in ECS

ECS and RS• K

• Na

• Ca

• Mg

• Al

• Zn

• Fe

• Sn

• Pb

• Cu

• Hg

• Ag

• Au

(RS) C

(RS) H

H (ECS)

Differences between electrolytic cell and voltaic/chemical cell

• Electrolytic cell• Oxidation occur at

positive electrode • because negative

ions • released electrons

here

• Chemical cell cell• Oxidation occur at

negative electrode• because metal

atom • release electrons

here

Differences between electrolytic cell and voltaic/chemical cell

• Electrolytic cell• Reduction occur at

negative electrode • because positive

ions • gain electrons here

• Chemical cell cell• Reduction occur at

positive electrode• because positive

ions • gain electrons here