Answer:
250 ml of the 75% mixture are needed to obtain the desired solution.
Step-by-step explanation:
Since I need a 70% alcohol solution, and on hand, I have a 40 mL of a 35% alcohol mixture, and I also have 75% alcohol mixture, to determine how much of the 75% mixture will you need to add to obtain the desired solution, the following calculation must be performed:
100 x 0.75 + 0 x 0.35 = 75
90 x 0.75 + 10 x 0.35 = 71
89 x 0.75 + 11 x 0.35 = 70.6
87.5 x 0.75 + 12.5 x 0.35 = 70
12.5 = 40
87.5 = X
87.5 x 40 / 12.5 = X
3,500 / 12.5 = X
280 = X
Therefore, 250 ml of the 75% mixture are needed to obtain the desired solution.
