What amount of pure acid must be added to 600 mL of a 40% acid solution to produce a 60% acid solution?

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.

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it's all four options.