vher,
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
1 a Redox reaction b Not a redox reaction c Redox reaction d Redox reaction
2 a Oxidation: Fe(s) Fe2+(aq) + 2e– Reduction: Ag+(aq) + e– Ag(s) Overall equation: Fe(s) + 2Ag+(aq) Fe2+(aq) + 2Ag(s) b Oxidation: Mg(s) Mg2+(aq) + 2e– Reduction: Cu2+(aq) + 2e– Cu(s) Overall equation: Mg(s) + Cu2+(aq) Mg2+(aq) + Cu(s) c No reaction. Iron cannot displace the more reactive zinc from solution. d Overall equation: Cu(s) + 2Ag+(aq) Cu2+(aq) + 2Ag(s)
Review Exercise 9.2
1 a –2 b 0 c +4 d +6 e +6 f –2
2 a NH3, ammonium salts b N2 c N2O d NO e HNO2, N2O3, nitrites f HNO3, nitrates
4 a Cr2O72–(aq) + 8H+(aq) + 3SO32–(aq) 2Cr3+(aq) + 4H2O(l) + 3SO42–(aq) b Cu(s) + 2NO3–(aq) + 4H+(aq) Cu2+(aq) + 2NO2(g) + 2H2O(l) c 2MnO4–(aq) + 16H+(aq) + 10Br–(aq) 2Mn2+(aq) + 8H2O(l) + 5Br2(aq)
5 a 2MnO4–(aq) + 2H2O(l) + 5SO2(g) 2Mn2+(aq) + 4H+(aq) + 5SO42–(aq) b Cr2O72–(aq) + 14H+(aq) + 6Fe2+(aq) 2Cr3+(aq) + 7H2O(l) + 6Fe3+(aq) c Zn(s) + SO42–(aq) + 4H+(aq) Zn2+(aq) + SO2(g) + 2H2O(l)
Review Exercise 9.3
1 Direction of electron flow: from iron half-cell to copper half-cell
4 b Cathode: platinum. Anode: zinc c Cathode: 2H+(aq) + 2e– H2(g) Anode: Zn(s) Zn2+(aq) + 2e– e Electron flow – through the wire from the Zn electrode to the Pt electrode
Review Exercise 9.4
1 c Overall equation: Pb(s) + 2Ag+(aq) Pb2+(aq) + 2Ag(s) e 0.93 V (under standard conditions)
2 a i Ag+ is the strongest oxidant. ii Electrons flow from tin (anode) to silver (cathode). iii Oxidation: Sn(s) Sn2+(aq) + 2e– Reduction: Ag+(aq) + e– Ag(s) iv Sn(s) + 2Ag+(aq) Sn2+(aq) + 2Ag(s) v Anode: tin. Cathode: silver vi 0.94 V b i Br2 is the strongest oxidant. ii Electrons flow from the magnesium towards the bromine half-cell. iv Mg(s) + Br2(aq) Mg2+(aq) + 2Br–(aq) v Anode: magnesium. Cathode:
A complete set of fully worked solutions is contained in the Chemistry for WA 2 Solutions Manual.
Review Exercise 9.1
1 a Redox reaction b Not a redox reaction c Redox reaction d Redox reaction
2 a Oxidation: Fe(s) Fe2+(aq) + 2e– Reduction: Ag+(aq) + e– Ag(s) Overall equation: Fe(s) + 2Ag+(aq) Fe2+(aq) + 2Ag(s) b Oxidation: Mg(s) Mg2+(aq) + 2e– Reduction: Cu2+(aq) + 2e– Cu(s) Overall equation: Mg(s) + Cu2+(aq) Mg2+(aq) + Cu(s) c No reaction. Iron cannot displace the more reactive zinc from solution. d Overall equation: Cu(s) + 2Ag+(aq) Cu2+(aq) + 2Ag(s)
Review Exercise 9.2
1 a –2 b 0 c +4 d +6 e +6 f –2
2 a NH3, ammonium salts b N2 c N2O d NO e HNO2, N2O3, nitrites f HNO3, nitrates
4 a Cr2O72–(aq) + 8H+(aq) + 3SO32–(aq) 2Cr3+(aq) + 4H2O(l) + 3SO42–(aq) b Cu(s) + 2NO3–(aq) + 4H+(aq) Cu2+(aq) + 2NO2(g) + 2H2O(l) c 2MnO4–(aq) + 16H+(aq) + 10Br–(aq) 2Mn2+(aq) + 8H2O(l) + 5Br2(aq)
5 a 2MnO4–(aq) + 2H2O(l) + 5SO2(g) 2Mn2+(aq) + 4H+(aq) + 5SO42–(aq) b Cr2O72–(aq) + 14H+(aq) + 6Fe2+(aq) 2Cr3+(aq) + 7H2O(l) + 6Fe3+(aq) c Zn(s) + SO42–(aq) + 4H+(aq) Zn2+(aq) + SO2(g) + 2H2O(l)
Review Exercise 9.3
1 Direction of electron flow: from iron half-cell to copper half-cell
4 b Cathode: platinum. Anode: zinc c Cathode: 2H+(aq) + 2e– H2(g) Anode: Zn(s) Zn2+(aq) + 2e– e Electron flow – through the wire from the Zn electrode to the Pt electrode
Review Exercise 9.4
1 c Overall equation: Pb(s) + 2Ag+(aq) Pb2+(aq) + 2Ag(s) e 0.93 V (under standard conditions)
2 a i Ag+ is the strongest oxidant. ii Electrons flow from tin (anode) to silver (cathode). iii Oxidation: Sn(s) Sn2+(aq) + 2e– Reduction: Ag+(aq) + e– Ag(s) iv Sn(s) + 2Ag+(aq) Sn2+(aq) + 2Ag(s) v Anode: tin. Cathode: silver vi 0.94 V b i Br2 is the strongest oxidant. ii Electrons flow from the magnesium towards the bromine half-cell. iv Mg(s) + Br2(aq) Mg2+(aq) + 2Br–(aq) v Anode: magnesium. Cathode: