SOLUTION: What quantity of pure acid must be added to 400 mL of a 40% acid solution to produce a 75% acid solution

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Question 629837: What quantity of pure acid must be added to 400 mL of a 40% acid solution to produce a 75% acid solution
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = ml of pure acid needed
+.4%2A400+=+160+ ml of acid in 40% solution
+%28+x+%2B+160+%29+%2F+%28+x+%2B+400+%29+=+.75+
+x+%2B+160+=+.75%2A%28+x+%2B+400+%29+
+x+%2B+160+=+.75x+%2B+300+
+.25x++=+140+
+x+=+560++
560 ml of pure acid must be added
check:
+%28+x+%2B+160+%29+%2F+%28+x+%2B+400+%29+=+.75+
+%28+560+%2B+160+%29+%2F+%28+560+%2B+400+%29+=+.75+
+720+%2F+960+=+.75+
+720+=+.75%2A960+
+720+=+720+
OK