CHEMISTRY 12 – OXIDATION #S AND REDOX REACTIONS WORKSHEET
1) Determine the oxidation number of the bold element in the following substances: (21 marks)
MnO4-
I2
S2O82-
Cu2+
Fe3O4
Na2S2O3
Na2O2
CaC2O4
C2 H3 O2 -
Cr(H2O)4Br2+
Mo6Cl12
H4As2O7
Cr2O72-
H2AsO4-
C2H5OH
H4P2O7
Ru(OH)22+
Na2Cr2O7
Ca2+
O2
(NH4)2MoO4
2) Classify the following reactions as oxidation, reduction or neither: (14 marks)
2 SO42- → S2O82-
C2H5OH → C2H4O2
ClO- → ClO3-
Cr3+ → Cr2O72-
NO2 → N2O4
MnO2 → Mn2O3
Cr3+ → Cr2+
ClO3- → ClO2
H3PO3 → H3PO4
CaO → Ca
IO3- → I2
MnO4- → Mn2+
ClO3- → ClO4-
NO2 → NO3-
3) Consider the following equation:
2 NO2 → N2O4
a) Does the above represent a redox reaction? (0.5 marks)
b) Explain. (1.5 marks)
4) Consider the following redox reaction:
MnO4- + 5 CH3CHO + 6 H+ → 5 CH3COOH + 2 Mn2+ + 3 H2O
a) Which species is losing electrons? (1 mark)
b) Which species is gaining electrons? (1 mark)
5) Consider the following equation:
Pt + 10 H+ + 6 Cl- + 4 NO3- → H2PtCl6 + 2 N2O4 + 4 H2O
a) Does the above represent a redox reaction? (0.5 marks)
b) Explain. (1.5 marks)
6) Consider the following redox reaction: (1 mark)
C2H5OH + 2 Cr2O72- + 16 H+ → 2 CO2 + 4 Cr3+ + 11 H2O
Each carbon atom loses
2 electrons
4 electrons
6 electrons
12 electrons
7) Consider the following redox reaction:
MnO4- + 5 Fe2+ + 8 H+ → Mn2+ + 5 Fe3+ + 4 H2O
(a) Which species is losing electrons? (1 mark)
(b) Which species is gaining electrons? (1 mark)
8) Which species is gaining electrons in the following redox reaction? (1 mark)
Br2 + SO2 + Na2SO4 + 2 H2O → 2 H2SO4 + 2 NaBr
9) Which species is undergoing oxidation in the following redox reaction? (1 mark)
Pt + 10 H+ + 6 Cl- + 4 NO3- → H2PtCl6 + 2 N2O4 + 4 H2O
10) Which species is undergoing reduction in the following redox reaction? (1 mark)
Pt + NO3- + Cl- → PtCl62- + NO + H2O
11) Which species loses electrons in the following redox reaction? (1 mark)
2 Cr3+ + 3 Cl2 + 7 H2O → Cr2O72- + 6 Cl- + 14 H+
12) Consider the following redox reaction: (1 mark)
3 C3H8O + 2 CrO3 + 3 H2SO4 → 3 C3H6O + 6 H2O + Cr2(SO4)3
Each chromium atom
Gained 2 electrons
Lost 2 electrons
Gained 3 electrons
13) Which species is undergoing reduction in the following redox reaction? (1 mark)
2 Cr3+ + 3 Cl2 + 7 H2O → Cr2O72- + 6 Cl- + 14 H+
14) Which species loses electrons in the following redox reaction? (1 mark)
Pt + NO3- + Cl- → PtCl62- + NO + H2O
Lost 3 electrons
15) Electrons are lost by the (1 mark)
reducing agent as it
undergoes oxidation
reducing agent as it
undergoes reduction
oxidizing agent as it
undergoes oxidation
oxidizing agent as it
undergoes reduction
oxidized as it loses
electrons
oxidized as it gains
electrons
16) An oxidizing agent is (1 mark)
reduced as it loses
electrons
reduced as it gains
electrons
17) Chlorine gas is a stronger oxidizing agent than silver sulphide. What is meant by the term stronger
oxidizing agent? (1 mark)
18) Al (s) is a stronger reducing agent than Cr (s). What is meant by the term stronger reducing agent?
(1 mark)
19) Which of the following is the strongest reducing agent? (1 mark)
Cu+
Pb
Ca
F2
20) Which of the following is the strongest oxidizing agent? (1 mark)
Br2
H2Se
Ag+
SO42-
21) The acidified substances H2O2, H3PO4 and H2SO3 in order of increasing strengths as oxidizing
agents are: (1 mark)
H2O2, H3PO4, H2SO3
H2SO3, H3PO4, H2O2
H3PO4, H2SO3, H2O2
H2O2, H2SO3, H3PO4
22) Which of the following is the weakest oxidizing agent? (1 mark)
Cu2+
Pb2+
Ni2+
Sn2+
23) Which of the following is the strongest reducing agent? (1 mark)
H2 S
H2 O
H2Se
H2Te
24) List the ions Co2+, Cu2+ and Zn2+ in order from strongest to weakest oxidizing agents. (1 mark)
Zn2+ > Co2+ > Cu2+
Co2+ > Cu2+ > Zn2+
Cu2+ > Zn2+ > Co2+
Cu2+ > Co2+ > Zn2+
25) Which of the following is the weakest reducing agent? (1 mark)
Co
Cu
Ca
Cr
26) Which of the following is the strongest oxidizing agent? (1 mark)
BrO3-
ClO4-
S2O82-
Cr2O72-
27) Which of the following is the strongest reducing agent? (1 mark)
Sn2+
Fe2+
Au3+
Mn2+
28) Identify the reducing agent in the following reactions: (8 marks)
Zn + 2 MnO2 + 2 H2O → Zn(OH)2 + 2 MnO(OH)
12 H+ + 2 IO3- + 10 Fe2+ → 10 Fe3+ + I2 + 6 H2O
Fe2O3 + 3 CO → 2 Fe + 3 CO2
Hg2+ + Cu → Hg + Cu2+
Co + SO42- + 4 H+ → Co2+ + H2SO3 + H2O
2 Fe + 3 Cu(NO3)2 → 2 Fe(NO3)3 + 3 Cu
3 NO + SO42- + Fe3+ + 2 H2O → FeS + 3 NO3- + 4 H+
Sn2+ + MnO4- → Sn4+ + Mn2+
29) Identify the oxidizing agent in the following reactions: (8 marks)
Pb + PbO2 + 4 H+ + 2 SO42- → 2 PbSO4 + 2 H2O
Ga3+ + 3 Rb → 3 Rb+ + Ga
3 As2O3 + 4 NO3- + 7 H2O + 4 H+ → 6 H3AsO4 + 4 NO
6 H+ + 6 I- + ClO3- → 3 I2 + 3 H2O + Cl3 NO + SO42- + Fe3+ + 2 H2O → FeS + 3 NO3- + 4 H+
Co + SO42- + 4 H+ → Co2+ + H2SO3 + H2O
12 H+ + 2 IO3- + 10 Fe2+ → 10 Fe3+ + I2 + 6 H2O
Hg2+ + Cu → Hg + Cu2+