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Dr. Jekyll has 180 mL of solution that is acid. How many mL of the solution must be replaced with pure acid in order to have a solution that is acid?54:

 

I was thinking that the ratio would be 36:144 for the 20% of acid and that the ratio for the 30% acid would be 54:126. HOWEVER. I forgot that the solutions are MIXED so i can't jsut do 54-36=18. Could someone introduce another way to solve this?

 Dec 3, 2022
 #1
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What percent of the 180 mL solution is acid? Is it 20% and you want to raise to 30%? Clarify your question.

 Dec 3, 2022
 #2
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180 x 0.20 ==36 mL of acid and 144 mL of water
180 x 0.30 ==54 mL of acid and 126 mL of water.
S==Solution


[36 - S] / [144 - S] ==54 / 126, solve for S
S ==-45 mL

180 - 45 ==135 mL of solution left


A ==Acid
[0.20 * 135] + A ==0.30 * [ 135 + A], solve for A


Acid ==19+2/7 mL of Acid to give a solution of 30% Acid.

 

Check:[0.20 * 135 + 19 2/7]==46+2/7 mL of Acid

            135 solution + 19 2/7==154 + 2/7 mL of solution

            [46 2/7] / [154 2/7] ==30%

 Dec 3, 2022

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