SOLUTION: If you wish to increase the percentage of acid in 50 mL of a 15% acid solution to 25% acid, how much pure acid must you add?

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Question 757087: If you wish to increase the percentage of acid in 50 mL of a 15% acid solution to 25% acid, how much pure acid must you add?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +x+ = ml of acid to be added
+.15%2A50+=+7.5+ ml of acid in 15% solution
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+%28+7.5+%2B+x+%29+%2F+%28+50+%2B+x+%29+=+.25+
+7.5+%2B+x+=+.25%2A%28+50+%2B+x+%29+
+7.5+%2B+x+=+12.5+%2B+.25x+
+.75x+=+12.5+-+7.5+
+.75x+=+5+
+x+=+6.667+
6.667 ml of pure acid must be added
check:
+%28+7.5+%2B+x+%29+%2F+%28+50+%2B+x+%29+=+.25+
+%28+7.5+%2B+6.667+%29+%2F+%28+50+%2B+6.667+%29+=+.25+
+14.1667+%2F+56.667+=+.25+
+14.1667+=+14.1667+
OK