SOLUTION: A chemist has 500L of a 15% acid solution. How much pure acid should be added to make a 20% acid solution?

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Question 564653: A chemist has 500L of a 15% acid solution. How much pure acid should be added to make a 20% acid solution?

Answer by Maths68(1474) About Me  (Show Source):
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Solution A
Amount = 500 liters
Concentration =15% =0.15
Solution B
Amount = x
Concentration =100% = 1
Resultant Solution
Amount =500+x
Concentration =20%=0.2
[Amount Solution A * Concentration A] + [Amount Solution B * Concentration of B] = Amount of Resultant * Concentration of resultant
(500)(0.15)+(x)(1)=(500+x)(.02)
75+1x=100+0.2x
1x-0.2x=100-75
0.8x=25
0.8x/0.8=25/8
x=20
He should add 20 liters of pure acide to make a 20% acid solution?