[birkato]

Hi,

Can someone tell me what I am doing wrong here.  I want to use 12.5% bleach in 200,000 gal of water to create a 1200ppm Hypochlorite concentration.  

200,000gal H2O  *8.34/18.02 = 92,623 lbmol

0.0012 (92,623 lbmol) = 111.15 lbmol of NaClO

111.15 lbmol NaClO * 72.45 lb/lbmol = 8052.8 lb of NaClO needed

8052.8 lb NaClO / 0.125 = 64,422 lb of 12.5% NaClO solution.

assuming 9.2 lb/gal for the solution...

64,422 lb solution / 9.2 = 7018 gal of 12.5% bleach is what I come up with.

*****

Now I have read on "How stuff works.com" that a 1 gallon bottle of 5.25% bleach will provide 1 ppm in 60,000 gal of water.  If this is true then 1200 gal will provide 1200 ppm for 60k gal.

1200 gal bleach * 200,000gal water/60,000 gal water = 4000 gal of 5.25%

4000 gal * 5.25/12.5 = 1680 gal of 12.5% bleach which is way off from my number above.

 

Can some chemical wizzard tell me what I am doing wrong here?  Or is the second calc wrong?

[themark]

Hello,

In your second step, you calculated a mole fraction rather than the mass fraction.  the second solution gives a mass fraction.

hope this helps