Oxidisers and reducers experiment part A please answer question...?

Question

Part: Oxygen

most people are aware that air and moisture can bring about rusting aof iron and steel. This is because oxygen dissolves in water and acts as an oxidiser in aqueous solution.

aim: to observe the oxidation of Fe2+ to Fe3+ by oxygen in aqueous solution.

appsrstus: two test tubes, test tube rack, access to a fresh suspension of iron(II) hydroxide and a suspension of iron(III) hydroxide.

method: 1. obtain approx 3ml of each suspension and note their their colours. (the colours are due to the iron(II) and iron(III) ions)

2. Shake both test tubes vigorously from side to side for several minutes to aerate the water with oxygen and record any changes in colour.

3. As the colour of iron(II) tuve approaches that of iron(III) tube, stop shaking.

Questions:

1. the half-equation for the ibserved change is:

Fe(OH)2(s) + OH- --> Fe(OH)3(s) + e-

a) why is this termed oxidation?

b) what was the purpose of the iron(III) hydroxide test tube?

2. oxygen acts as an oxidiser indirectly as it dissolves in water. The reduction half equation is:

O2(g) + 2H2O + 4e- ---> 4OH- (aq)

write a balanced overall equation for the reaction.

Answer 1

1. the half-equation for the ibserved change is:

Fe(OH)2(s) + OH- --> Fe(OH)3(s) + e-

a) why is this termed oxidation?

because the Fe+2 lost an electron in becoming Fe+3

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b) what was the purpose of the iron(III) hydroxide test tube?

to give youi something to oxidize, which would change in color when it did get oxidized

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2. oxygen acts as an oxidiser indirectly as it dissolves in water. The reduction half equation is:

O2(g) + 2H2O + 4e- ---> 4OH- (aq)

write a balanced overall equation for the reaction.

since Fe(OH)2(s) + OH- --> Fe(OH)3(s) + e-   only loses 1 electron, we four thimes this reaction to have the same # of electrons taken as lost:

4 Fe(OH)2(s) + 4 OH- --> 4 Fe(OH)3(s) + 4 e-  lost

O2(g) + 2H2O + 4e- taken   ---> 4OH- (aq)

combining them:

4 Fe(OH)2(s) + 4 OH- & O2(g) + 2H2O--> 4 Fe(OH)3(s) & 4OH-

simplifying:

4 Fe(OH)2(s)  & O2(g) + 2H2O--> 4 Fe(OH)3(s)