SOLUTION: A chemist has 100 cc of 20% acid, the rest being water. She adds pure acid to make the solution 33 1/3% acid. How many ccs of water must she then add to return it to 20% acid?

Question 319262: A chemist has 100 cc of 20% acid, the rest being water. She adds pure acid to make the solution 33 1/3% acid. How many ccs of water must she then add to return it to 20% acid?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A chemist has 100 cc of 20% acid, the rest being water. She adds pure acid to make the solution 33 1/3% acid. How many ccs of water must she then add to return it to 20% acid?
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Equation:
acid + acid = acid
0.20*100 + 1x = 0.333(100+x)
Multiply thru by 1000 to get:
200*100 + 1000x = 333*100 + 333x
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667x = 133*100
x = 19.94 cc (amt. of pure acid needed for the mixture)
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Cheers,
Stan H.
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