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Topics: Electrochemistry, Electrolysis, Redox Pages: 4 (866 words) Published: June 25, 2014
9 Oxidation and reduction
A complete set of fully worked solutions is contained in the Chemistry for WA 2 Solutions Manual.

Review Exercise 9.1
1aRedox reaction
bNot a redox reaction
cRedox reaction
dRedox reaction
2aOxidation: Fe(s)  Fe2+(aq) + 2e–
Reduction: Ag+(aq) + e– Ag(s)
Overall equation:Fe(s) + 2Ag+(aq)  Fe2+(aq) + 2Ag(s)
bOxidation: Mg(s)  Mg2+(aq) + 2e–
Reduction: Cu2+(aq) + 2e– Cu(s)
Overall equation:Mg(s) + Cu2+(aq)  Mg2+(aq) + Cu(s)
cNo reaction. Iron cannot displace the more reactive zinc from solution. dOverall equation:Cu(s) + 2Ag+(aq)  Cu2+(aq) + 2Ag(s)

Review Exercise 9.2
1a–2
b0
c+4
d+6
e+6
f–2
2aNH3, ammonium salts
bN2
cN2O
dNO
eHNO2, N2O3, nitrites
fHNO3, nitrates
4aCr2O72–(aq) + 8H+(aq) + 3SO32–(aq)  2Cr3+(aq) + 4H2O(l) + 3SO42–(aq) bCu(s) + 2NO3–(aq) + 4H+(aq)  Cu2+(aq) + 2NO2(g) + 2H2O(l) c2MnO4–(aq) + 16H+(aq) + 10Br–(aq)  2Mn2+(aq) + 8H2O(l) + 5Br2(aq) 5a2MnO4–(aq) + 2H2O(l) + 5SO2(g)  2Mn2+(aq) + 4H+(aq) + 5SO42–(aq) bCr2O72–(aq) + 14H+(aq) + 6Fe2+(aq)  2Cr3+(aq) + 7H2O(l) + 6Fe3+(aq) cZn(s) + SO42–(aq) + 4H+(aq)  Zn2+(aq) + SO2(g) + 2H2O(l)

Review Exercise 9.3
1Direction of electron flow: from iron half-cell to copper half-cell 4bCathode: platinum. Anode: zinc
cCathode: 2H+(aq) + 2e–  H2(g)
Anode: Zn(s)  Zn2+(aq) + 2e–
eElectron flow – through the wire from the Zn electrode to the Pt electrode

Review Exercise 9.4
1cOverall equation:Pb(s) + 2Ag+(aq)  Pb2+(aq) + 2Ag(s) e0.93 V (under standard conditions)
2aiAg+ is the strongest oxidant.
iiElectrons flow from tin (anode) to silver (cathode).
iiiOxidation: Sn(s)  Sn2+(aq) + 2e–
Reduction: Ag+(aq) + e– Ag(s)
ivSn(s) + 2Ag+(aq)  Sn2+(aq) + 2Ag(s)
vAnode: tin. Cathode: silver
vi0.94 V
biBr2 is the strongest oxidant.
iiElectrons flow from the magnesium towards the bromine half-cell. ivMg(s) + Br2(aq)  Mg2+(aq) + 2Br–(aq)
vAnode: magnesium. Cathode: platinum...
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