3. a) Complete the half
equations by balancing it and identify each half-reaction as either oxidation (O) or reduction (R) reaction.
(i) Na (s) ®
Na+ (aq)
(ii) Mg2+(aq) ®
Mg (s)
(iii) Fe (s) ®
Fe3+(aq)
(iv) Cl- (aq) ® Cl2
(g)
(v) K(s) ® K+ (aq)
(vi)
O2 (g) ® O2-
(aq)
vii) F- (aq) ® F2 (g)
(viii) Cu 2+ (aq) ® Cu(s)
(ix)
S (s) ® S2-
(aq)
(x) H2 (g) ® H+ (aq)
4 Consider the incomplete reaction (partial ionic
equation) given below:
A) Cu2+ + Zn ® Zn2+ + Cu
i) Give the two half
equations for this reaction; oxidation + reduction
ii) Identify the chemical substance (species)
that has undergone oxidation
iii) Identify the chemical substance (species)
that has undergone reduction
iv) Identify (from the reactants) the
oxidising agent (oxidant) in this reaction;
v) Identify (from the reactants) the reducing
agent (reductant) in this reaction
REPEAT QUESTIONS I---V FOR THE
FOLLOWING REACTIONS (Unbalanced):
B) Cl2 (aq) chlorine
water + Br- (aq) ® Br2(aq) +Cl- (aq)
C) Fe (s) +
Ag+(aq) ® Ag (s) +
Fe2+ (aq)
D) Mg (s) + S (s) ® MgS (s)
E) S(s) +
O2 (g) ® SO2
(g)
F) Al(s) +
O2 (g) ® Al2O3 (s)
G) Pb2+(aq) +
Mg (s) ® Mg2+
(aq) + Pb (s)
H) Al (s) +
Fe 2+ (aq) ® Al3+(aq) +
Fe (s)
5 )
Identify the following (some are half reactions) as involving either oxidation or reduction or
neither:
a) Mg (s) ®
Mg2+(aq) +2e-
b) O2
(g) + 2H2O
(l) + 4e- ® 4OH- (aq)
c) Cu2+(aq) + 2e- ® Cu(s)
d) Fe(s)
® Fe2+ (aq) + 2e-
6)
Write the oxidation number for each element in the following species
a) CO b) SO3 c) H3PO4 d) Cr2O7
2- e) ClO-
