Question

How many ml of 30 percent acid should be added to pure acid to make 80 ml of 35 percent acid?

Answer 1

Let x = number of ml of 60% acid

Since we are making up 50mL of solution, the amount of pure acid will be (50 - x)

x mL of 60% acid plus (50 - x )mL of 100% acid = 50 mL of 85% acid

0.60x + 1.00 (50 - x ) = 0.85(50)

0.60x + 50 - 1.00 x = 42.5

0.60x -1.00 x = -7.5

-0.40x = -7.5

x = 18.75

You need to add 18.75 mL of 60% solution to pure acid to make 50 mL of 85% acid.

Check: (18.75)(0.60) + 1.00(50-18.75) = 50(0.85)

11.25 + 31.25 = 42.5