electrolysis of nitric acid

HNO3: Oxygen gas is evolved at the anode, and hydrogen gas at the cathode.

In the solution, HNO3 is ionized to give H+(aq) and NO3-(aq) ions, H2O is slightly self-ionized to give H+(aq) and OH-(aq) ions.

Anode: NO3-(aq) and OH-(aq) ions migrate to the anode. OH-(aq) ion is preferentially discharged to give oxygen gas because OH-(aq) ion is oxidized much more readily than NO3-(aq) ion.
4OH-(aq) → 2H2O(l) + O2(g) + 4e-

Cathode: H+(aq) ion migrates to the cathode, and is discharged to give hydrogen gas.
2H+(aq) + 2e- → H2(g)


H2SO4: Oxygen gas is evolved at the anode, and hydrogen gas at the cathode.

In the solution, H2SO4 is ionized to give H+(aq) and SO42--(aq) ions, H2O is slightly self-ionized to give H+(aq) and OH-(aq) ions.

Anode: SO42-(aq) and OH-(aq) ions migrate to the anode. OH-(aq) ion is preferentially discharged to give oxygen gas because OH-(aq) ion is oxidized much more readily than SO42-(aq) ion.
4OH-(aq) → 2H2O(l) + O2(g) + 4e-

Cathode: H+(aq) ion migrates to the cathode, and is discharged to give hydrogen gas.
2H+(aq) + 2e- → H2(g)


NaOH: Oxygen gas is evolved at the anode, and hydrogen gas at the cathode.

In the solution, NaOH is ionized to give Na+(aq) and OH-(aq) ions, H2O is slightly self-ionized to give H+(aq) and OH-(aq) ions.

Anode: OH-(aq) ion migrates to the anode, and is discharged to give oxygen gas.
4OH-(aq) → 2H2O(l) + O2(g) + 4e-

Cathode: Na+ and H+(aq) ions migrate to the cathode. H+(aq) ion is preferentially discharged to give hydrogen gas because H+(aq) ion is reduced much more readily than Na+(aq) ion.
2H+(aq) + 2e- → H2(g)


Farmer would not use sodium hydroxide to reduce soil acidity, because
(1) sodium hydroxide is very corrosive.
(2) farmer can obtain calcium oxide by heating limestone, shells or egg-shells.
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2009-06-20 18:57:29 補充：
In electrolysis of HNO3, no NO is evolved.

Besides, there is absolutely no such compound SO4.

HNO3: H2(cathode), O2+NO(anode)
H2SO4: H2(cathode), O2+SO4(anode)
NaOH: H2(cathode), O2(anode)

Will farmers use sodium hydroxide to reduce soil acidity?
No!!!!!!!! Sodium hydroxide solution is very corrosive, farmers will use calcium hydroxide instead of sodium hydroxide.

2009-06-20 22:27:10 補充：
打錯, 係SO42-