[MCL99]

Hi,
I would like to find out how the below was calculated:
- The required concentration of the final solution is 1mg/l as Cl2
- The chemical used: 15% (w/w) sodium hypochlorite
- 1,000,000l of water is used
Answer: 5.6l of chemical (sodium hypochlorite) is needed to satisfy the above water usage.

Look forward to giving me some hints on how it should be solved/approached, thank you in advance.

[Borek]

Please read the forum rules. You have to show your attempts at answering the question/solving the problem to receive help, it is a forum policy.

There are two parts to this problem: one is a simple dilution, the other is equivalence between hypochlorite and Cl₂. Do you know how to approach this kind of calculations?

[MCL99]

Hi, thanks for your reply. I forgot to mention in the first post that I was trying to calculate it myself, but with no luck.
 
I was using this equation: C1*V1 = C2*V2, however, I was not sure which constituents I should quote and it still did not work.
For the equivalence between NaOCl and Cl2: did you mean 1 mol Cl2 = 1 mol NaOCl which quals to 2.08 mg/l of NaOCl? If so, I would not know where to apply it either.

Any help will be appreciated. Thanks

[Borek]

For the equivalence between NaOCl and Cl2: did you mean 1 mol Cl2 = 1 mol NaOCl which quals to 2.08 mg/l of NaOCl?

Close, but no.

NaOCl is in equilibrium with water and NaOH, can you try to write a reaction equation? Once you balance it, you will know what is the molar ratio between Cl₂ and NaOCl. This will tell you how much NaOCl is required to give the solution equivalent of 1 mg of Cl₂ per L.

[MCL99]

I have attached the reaction and calculation, but I am still not getting the 5.6l of chemical needed per 10^6l of water.