Question

how many liters of a 40% acid solution must be added to 12 liters of a 20% solution to obtain a 25% solution​

Answer 1

Answer:

The answer is 4 liters.

Step-by-step explanation:

We want a final 25% solution, which means that the solvent should constitute 25 percent of all the liters of solution.

Let us call $x$ the litres of 40% solution, so when they are added to the 12 litres of 20% solution, the total litres of the new solution are:

$x+12$

of these liters, 25% must be the solvent:

$N=0.25(x+12)$

Now for the 40% solution, the liters of the solvent are $0.4x$, and for the 20% liter solution, the liters of solve are $0.2*12=2.4$ liters. Thus the total liters $N$ of the solvent are

$N=0.4x+2.4$

Therefore

$N=0.4x+2.4=0.25(x+12)$

$\therefore x=4\:litres$