Answer:
You need to add 300mL of a pure acid to produce a 60% acid solution.
Explanation:
Pure acid is a 100% acid. If you suppose X is the volume addition of the pure acid it is possible to write:
100%X + 600×40% = (600+X)60% (M₁V₁=M₂V₂)
100X + 24000 = 36000 + 60x
40X = 12000
X = 300
That means you need to add 300mL of a pure acid to produce a 60% acid solution.
I hope it helps!
