Balance equation 問題

To balance a chemical equation, the atoms on the both sides are balanced one by one. The usual method is to add two coefficients on both sides (for the first steps only) or one coefficient (for the other steps), in order to make numbers of a certain type of atom on both sides are equal.
Usually, if a type of atom appears once on each side, this type of atom should be balanced first.

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1. KOH + H2SO4 → K2SO4 + H2O
(1) Balance K: 2KOH + H2SO4 → 1K2SO4 + H2O
(2) Balance S: 2KOH + 1H2SO4 → 1K2SO4 + H2O
(3) Balance O: 2KOH + 1H2SO4 → 1K2SO4 + 2H2O
Answer: 2KOH + H2SO4 → K2SO4 + 2H2O

2. NaOCl → Na+ + Cl- + O2
(1) Balance O: 2NaOCl → Na+ + Cl- + 1O2
(2) Balance Cl: 2NaOCl → Na+ + 2Cl- + 1O2
(3) Balance Na: 2NaOCl → 2Na+ + 2Cl- + 1O2
Answer: 2NaOCl → 2Na+ + 2Cl- + O2

3. Cl2 + NH3 → NH4Cl + N2
(1) Balance H: Cl2 + 4NH3 → 3NH4Cl + N2
(2) Balance N: Cl2 + 4NH3 → 3NH4Cl + (1/2)N2
(3) Balance Cl: (3/2)Cl2 + 4NH3 → 3NH4Cl + (1/2)N2
(4) Both sides x2: 3Cl2 + 8NH3 → 6NH4Cl + 1N2
Answer: 3Cl2 + 8NH3 → 6NH4Cl + N2

(3/2)Cl2 同埋1/2個N2 點計出黎架?