Total = 36oz
Amount of 18% solution = x
Amount of 9% solution = 36 - x
Using the fact that (amount of solution) (percent HCl) = amount HCl we can set up an expression for the amount HCl in a mixture of 18% and 9% solutions with a total volume of 36oz.
Amount of HCl = x0.18 + (36 - x)0.09
If we divide this by the amount of solution we get percent HCl, and we have a target of 10% HCl. Now we have an equation to solve,
[x0.18 + (36 - x)0.09]/36 = 0.1
x0.09 + 3.24 = 3.6
.09x = 0.36
x = 4
Therefore,
4 ounces of 18% HCl solution and 32 ounces of 9% HCl solution
Check:
[(4.18) + (.0932)]/36 = 0.1?
0.1 = 0.1 Yes.
