[manuelgabriel]

I'm going to produce Sodium hypochlorite using electrolysis of NaCl solution. How much H2O and NaCl do I need for me to produce 1L of sodium hypocholrite with 8-10% concentration. And wit would be very helpful if you tell me how you arrived with the said answer. Thank you.

[Arkcon]

OK, lets try to figure this out.  You'll need to write a balanced chemical equation to begin with.  What are you starting with?  Can you write that on chemical shorthand?

[manuelgabriel]

I'm using electrolysis of NaCl and I'm hoping to come up with NaOCl

Basically, the chemical reaction would be

Cl2  +H2O  ==> ClO‾ + OH‾

NaCl + H20 ==>  Cl2 + H2 + NaOCl

OK, lets try to figure this out.  You'll need to write a balanced chemical equation to begin with.  What are you starting with?  Can you write that on chemical shorthand?

[Arkcon]

No, those aren't the reactions I was looking for.  You're sending an electric current through a solution of ions.  Something is going to be oxidized at the anode and send an e^- to the cathode, and the e^- will reduce something at the cathode.

[manuelgabriel]

Is there any way I could create 8-10% concentration of Sodium hypochlorite? I tried using electrolysis of NaCl but I only got 3% no matter how much NaCl I use. Thank you in advance.

[Burner]

Arkcon has told you to write chemical equations for the said NaCl to NaOCl reaction and you did it wrongly. You need to write a correct one because that helps you to do stoichiometry calculations to determine the amount of reactants you need.

Now, start again. Write the two balanced half-equations for the reaction. Be aware that there are electrons in a half-equation. Also, think carefully about which reactants will be attracted to the cathode and anode and which of them will actually oxidize/reduce.

[manuelgabriel]

From what I understand, NaOH should be liberated at the cathode while Chlorine gas at the anode. So the sodium ions are reduced and chloride ions are oxidized.

No, those aren't the reactions I was looking for.  You're sending an electric current through a solution of ions.  Something is going to be oxidized at the anode and send an e^- to the cathode, and the e^- will reduce something at the cathode.

[Burner]

From what I understand, NaOH should be liberated at the cathode while Chlorine gas at the anode. So the sodium ions are reduced and chloride ions are oxidized.

No. NaOH is not 'liberated' at the cathode, but they exist in the electrolyte after electrolysis. Sodium ions are present in NaOH and no sodium metal is formed, thus sodium ions are not reduced.

You are correct about that chloride ions are oxidized to form chlorine gas.

[vmelkon]

Probably the best way to do it is to buy Ca(ClO)2 from a store. This is available at the pool section. Add HCl.

Ca(ClO)2 + 4 HCl → CaCl2 + 2 Cl2 + 2 H2O

Lead the chlorine into a solution of NaOH.
2 NaOH + Cl2 → NaClO + NaCl + H2O

This is what I am doing right now. Make sure that joints are tight. Chlorine is toxic for your lungs.
Last time that I did it, my yield was 62% based on Ca(ClO)2.


Alternatively, you might be able to produce it via
Ca(ClO)2 + Na2SO4 → CaSO4(solid) + 2 NaClO

And then filter to remove the solid CaSO4.

The electrolysis method of NaCl doesn’t work very well.