A chemist has 100ml of 25% acid solution. How much of the solution does she need to drain and replace with 70% acid solution to obtain 100ml of 60% acid solution?

50% of the solution

Step-by-step explanation:

25% of 100 ml = 25

added to 70 % of (100 - x) = 70 - 0.7x

we need to add 25 + 70-0.7x to get = 100 ml 60% i. e 60

now,

solve for x

0.7x = 25+70-60

0.7x = 35

x = 35/0.7

x = 50 % of the solution she needs to drain

The chemist must drain 78 g of 25% acid solution and replace with 78 g of 70% acid.

Step-by-step explanation:

x = mass of the 25% acid the chemist must drain, Then we have, x = the mass, m of the 70% acid, 100-x=the mass of the 25% acid remaining, The operating equation is, Mass of acid in 25% + Mass of acid in 70% = Mass of acid in 60%, 0.25 (100-x) + 0.70 x=0.60*100, 25 - 0.25 x 0.70 x=60, 0.45 x = 35, x = 35/0.45, so we get, x=78 g.