[Iodine]

If one liter of commercial bleach contains about 40 grams of active chlorine, what is its molarity and concentration in percents?

If I need to make 1 liter of 2,5% sodium hypochlorite solution, how much commercial bleach and distilled water would I need?

[Borek]

Please read forum rules.

You have to show your attempts to receive help. This is a forum policy.

[Iodine]

Ok, Here's what I know:

Atomic masses:

Na = 22,99
Cl = 35,45 
O = 16

Molecular mass of NaOCl is: 22,99 + 35,45 + 16 = 74,44

One mole of NaOCl would contain 1 mole of Cl atoms (35,45 grams). If the solution contains 40 grams of Chlorine, then:

35,45 grams Cl  -     1 mole
40 grams Cl      -     x moles

x = (40 * 100) / 35,45 = 1,1283 moles of Cl in 1 liter of commercial bleach. (is this correct?). Therefore, the solution of commercial bleach is 1,1283 M.


Regarding the first question:


74,44 grams of NaOCl  contains 16 grams of Cl
x     grams of NaOCl  contains 40 grams of Cl

x = 186,1 grams of NaOCl is present in the 1 liter solution.


74,44 grams - 100 %
186,1 grams - x %

x = 250 % ?

250% seems too much, so where am I mistaken?

[Borek]

Therefore, the solution of commercial bleach is 1,1283 M.

That's OK.

74,44 grams of NaOCl  contains 16 grams of Cl

Check.

x     grams of NaOCl  contains 40 grams of Cl

x = 186,1 grams of NaOCl is present in the 1 liter solution.


74,44 grams - 100 %
186,1 grams - x %

x = 250 % ?

250% seems too much, so where am I mistaken?

What you did is something like percentage of hypocholorite in chlorine, not in the solution

It is not clear what the question asks about - percentage of what in what? Either JUST chlorine in the bleach solution (then to calculate precentage you just use 40 g and mass of 1L of solution - assume it is just 1 kg), or of sodium hypochlorite - than you have to convert mass of chlorine to mass of hypochlorite, but still assume 1 kg of solution.