Question

You need a 60% alcohol solution. On hand, you have a 225 mL of a 50% alcohol mixture. You also have 85% alcohol mixture. How much of the 85% mixture will you need to add to obtain the desired solution?

Answer 1

90 ml

Explanation:

225 ml of 50% solution contains:

• 225/2= 112.5 ml of alcohol and same amount of water

x ml of 85% alcohol mixture contains

• 0.85x ml of alcohol and 0.15x of water

we need 60% solution which will contain:

• (225+x)*0.6= 112.5+0.85x
• 135+0.6x= 112.5+0.85x
• 0.85x-0.6x= 135-112.5
• 0.25x= 22.5
• x=22.5/0.25
• x= 90 ml

so we require 90 ml of 85% solution added