Complete and balance each of the following reactions. If no reaction should occur, write 'NR'. Indicate physical states for all. Classify each reaction as redox, precipitation, gas-formation, or acid-base reaction.
a) Cu + H3PO4(aq) -> NR
b) K2SO4(aq) + Ba(C2H3O2)2(aq) -> 2KC2H3O2(aq) + BaSO4(s)
c) C2H4(g) + 3O2(g) -> 2CO2(g) + 2H2O(g)
d) Al(s) + FeI2(aq) -> NR
e) Ba(OH)2(aq) + H2C2O4(aq) -> NR