SOLUTION: A lab contains 24 ounces of iodine solution of strength 15%. How much pure iodine would you mix with it to get an iodine solution of strenth 25%?

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Question 270276: A lab contains 24 ounces of iodine solution of strength 15%. How much pure iodine would you mix with it to get an iodine solution of strenth 25%?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
In words:
(ounces of iodine in final solution)/(ounces of final solution) = 25%
Let x = ounces of pure iodine I need to add
given:
.15%2A24+=+3.6 ounces of iodine in 15% solution
-----------------------------------------------------
%283.6+%2B+x%29%2F%2824+%2B+x%29+=+.25
3.6+%2B+x+=+.25%2A%2824+%2B+x%29
3.6+%2B+x+=+6+%2B+.25x
.75x+=+6+-+3.6
.75x+=+2.4
x+=+2.4%2F.75
x+=+3.2
3.2 ounces of pure iodine must be added
check:
%283.6+%2B+x%29%2F%2824+%2B+x%29+=+.25
%283.6+%2B+3.2%29%2F%2824+%2B+3.2%29+=+.25
6.8%2F27.2+=+.25
6.8+=+.25%2A27.2
6.8+=+6.8
OK