A chemist needs to prepare 500 ml of copper-sulfate solution with a 15% concentration. She wishes to use a high concentration solution (60%) and dilute it with a low concentration solution (5%) in order to do this. How much of the 60% solution should she use round to the nearest whole number? Do not use units

She should use 91 mL of the 60% solution (rounded to the nearest whole number).

Step-by-step explanation:

The first step to solve this question is to write the correct equations system. The two variables are :

: The amount of high concentration solution (60%) (in mL).

: The amount of low concentration solution (5%) (in mL).

The first equation for the mixing is :

(I)

Where , and represent the percentages for , and the final 500 mL of copper-sulfate solution respectively.

The second equation is :

(II)

The equation (II) represents that the sum from the volumes of high and low concentration solution must be 500 mL.

The final step is to solve this equation system :

From (II) we find that :

(III)

If we use (III) in (I) :

≅

She should use 91 mL of the 60% solution (rounded to the nearest whole number).