SOLUTION: if a chemist has 40 ounces of a 25% acid solution, how much acid should be mixed with it to produce a new solution that is 40%

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Question 562273: if a chemist has 40 ounces of a 25% acid solution, how much acid should be mixed with it to produce a new solution that is 40%
Found 2 solutions by mananth, issacodegard:
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!

percent ---------------- quantity
Acid solution 25 ----------------40 ounces
Pure acid 100 ----------------x ounces
Mixture 40 ----------------40+x ounces

25*40+100x=40(40+x)
1000+100x=1600+40x
100x-40x=1600-1000
60x=600
/60
x=10 ounces of Pure acid

Answer by issacodegard(60) About Me  (Show Source):
You can put this solution on YOUR website!
Hi, let x be the volume of acid to be added. Let V be the volume of the new solution and V_a be the volume of the acid in the new solution.
Then,
V=40+x
V_a=(0.25)*40+(1.00)*x=10+x (since x is purely acid)
(0.40)V=V_a
To solve for x, we substitute to get,
(0.40)(40+x)=10+x
So by solving this last equation for x, we find x=10