Answer:
2 C2H6 + 7O2 => 6 H2O + 4 CO2
12HClO4 + P4O10 => 4 H3PO4 + 6Cl2O7
2 N2 + 5 O2 + 2 H2O => 4 HNO3
3 CaCl2 + 2 Na3PO4 => 1 Ca3(PO4)3 + 6 NaCl
4 FeS + 7 O2 => 2 Fe2O3 + 4 SO2
Explanation: Each equation is now balanced both in the reactant and product side.