SOLUTION: Pure acid is to be added to a 10% acid solution to obtain 54L of a 20% acid solution. What amounts of each should be used?

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Question 30192: Pure acid is to be added to a 10% acid solution to obtain 54L of a 20% acid solution. What amounts of each should be used?
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = amount of pure acid added.

So how much of the 10% acid was there? Easy... everything else to make up the 54litres...so (54-x).

Now we say BEFORE = AFTER

BEFORE is (1.00*x) + (0.10*(54-x))
AFTER is 0.20*54

so (1.00*x) + (0.10*(54-x)) = 0.20*54
x + 5.4 - 0.1x = 10.8
0.9x + 5.4 = 10.8
0.9x = 5.4
x = 5.4/0.9
x = 6 litres

So we need 6 litres of the pure acid and also 48 litres of the 10% acid solution.

jon.