SOLUTION: What quantity of pure acid must be added to 400 mL of a 25% acid solution to produce a 70% acid solution?

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Question 366076: What quantity of pure acid must be added to 400 mL of a 25% acid solution to produce a 70% acid solution?
Answer by nerdybill(7384) About Me  (Show Source):
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What quantity of pure acid must be added to 400 mL of a 25% acid solution to produce a 70% acid solution?
.
Let x = amount (mL) of pure acid to add
then
x + .25(400) = .70(400+x)
x + 100 = 280+.70x
.30x + 100 = 280
.30x = 180
x = 600 mL