[Roni]

No one can help me?

[Roni]

thank you!

[Roni]

Thank you

[Roni]

I think I understand now. 
please let me be sure I’m on it:
if I want to make a 100 g solution with 8% concentration of ingredient X.
But the ingredient is not pure, the purity is 75%.
so I calculate it:
ingredient X =    8%/75% = 10.66 g
water = 89.34 g

correct?

[Roni]

Ok, I’ll be careful. Do you have anything to say about my wrong calculation?

[Roni]

thanks!
I was thinking to use the formula C1V1=C2V2
 where C1 is a concentration of the stock solution (33%),
 V1 is a volume which I require,
C2 is concentration which I want to make (2.5%)
and V2 is the volume which I want to make.

for example, if I want to make 100mL of 2.5% H2O2 from 33% H2O2.  I use this formula and  I will find that I need to add 90.91 mL distilled water to 9.09 mL of 33% H2O2.
and because I need to add 10g of ingredient X, the water I will add will be 80.91 mL. 
The result I got is inaccurate