Question

You need a 35% alcohol solution. on hand, you have a 405 ml of a 30% alcohol mixture. you also have 80% alcohol mixture. how much of the 80% mixture will you need to add to obtain the desired solution?

Answer 1

You must add 45 mL of the 80 % alcohol to the 30 % alcohol to get a 35 % solution.

You can use a modified dilution formula to calculate the volume of 80 % alcohol

V1×C1 + V2×C2 = V3×C3

Let the volume of 80 % mixture 1 = x mL. Then the volume of the final 35 % mixture 3 = (405 + x ) mL

(x mL×80 % alc) + (405 mL×30 % alc) = (405 + x)mL × 35 % alc

80x + 12 150 = 14 175 + 35 x

45x = 2025

x = 2025/45 = 45