Chemistry
posted by Justin .
please help me balance these equations using the method of half reactions..
Na + HCL = NaCl + H2
Pb + PbO2 + H2SO4 = PbSO4 +H2O
Thank you, even a little help is appreciated.

Separate the two half reactions.
Na ==> Na^+ and
H^+ ==> H2
Balance the atoms (so we're comparing apples with apples when we start the electron loss and gain).
Na is ok.
2H^+ ==> H2
Do them one at at time.
Na ==> Na^+ + e
Next do the other one.
2H^+ + 2e ==> H2
Electron gain must equal electron gain so multiply Na half equn by 2 and H half equn by 1 so we have this.
2Na ==> 2Na^+ + 2e
2H^+ + 2e ==> H2 and add them.

2Na + 2H^+ + 2e ==> 2Na^+ + 2e + H2
Cancel the 2e on each side.
Now you can add the spectator ions.
2Na + 2HCl ==> 2NaCl + H2
voila!