Balancing Equations:
Given a chemical equation, the species themselves may not be changed. The subscripts
in the chemical formula of a compound may not be changed in order to balance the
equation. Only the number in front of the species is changed to show a difference in
number of atoms, number of moles, number of liters, etc.
For example, balance the equation given below:
_Al(HCO3)3 (s)  _Al2(CO3)3 (s) + _CO2 (g) + _H20 (g)
The order of steps below may be changed – this is only my recommendation:
1) do the cations first – so first balance the Al’s
There are two Al’s on the right, one on the left, so put a 2 in front of Al(HCO3)3(s)
2) do the C’s next – there are now 6 on the left and 3 in Al2(CO3)3 (s) – need 3 more, so
put a 3 in front of CO2(g)
3) have 6H’s on the left side of the equation, so put a 3 in front of H2O(g)
4) do the O’s last
5) count all atoms – it balances, so you are done!
Result:
2Al(HCO3)3 (s)  Al2(CO3)3 (s) + 3CO2 (g) + 3H20 (g)
Practice these:
1) HCl
+
2)
Fe2O3
3)
SO2
4)
I2
Zn
+
+
+

H2
C 
O2
Cl2
+
Fe


ZnCl2
+
SO3
ICl3
5) C2H3O2Cl + O2 => CO + H2O + Cl2(g)
6) CO2 + HCl  C2H3Cl3 + O2(g)
7) _AgNO3 + _ CaCl2
_ AgCl + _ Ca(NO3)2
CO2