SOLUTION: How many liters of pure acid should a chemist mix with 4 liters of a 10% acid solution to produce a solution that is 80% acid?

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Question 877874: How many liters of pure acid should a chemist mix with 4 liters of a 10% acid solution to produce a solution that is 80% acid?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +a+ = liters of pure acid needed
+.1%2A4+=+.4+ liters of acid in 10% solution
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+%28+a+%2B+.4+%29+%2F+%28+a+%2B+4+%29++=+.8+
+a+%2B+.4+=+.8%2A%28+a+%2B+4+%29+
+a+%2B+.4+=+.8a+%2B+3.2+
+.2a+=+2.8+
+a+=+14+
14 liters of pure acid should be added
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check:
+%28+a+%2B+.4+%29+%2F+%28+a+%2B+4+%29++=+.8+
+%28+14+%2B+.4+%29+%2F+%28+14+%2B+4+%29++=+.8+
+14.4+%2F+18+=+.8+
+14.4+=+.8%2A18+
+14.4+=+14.4+
OK