Identify which substance in the following equations has been oxidised and which substance has been reduced.
a. a 4Na(s)+O2(g)→2Na2O(s)
b. b 2Li(s)+2H2O(l)→2LiOH(aq)+H2(g)
c. c Fe2O3(s)+3CO(g)→2Fe(s)+3CO2(g)
d. d C2H4(g)+H2(g)→C2H6(g)
e. e 2NaBr(aq)+Cl2(aq)→2NaCl(aq)+Br2(aq)
f. f Cu(s)+2Ag+(aq)→Cu2+(aq)+2Ag(s)