mL of pure alcohol

Question

You need 25 % alcohol solution. On hand,you have a 975mL of a 5% alcohol mixture. How much pure alcohol will you need to add to obtain the desired solution

Answer 1

Yu have alcohol concentration of

0.05(975)

We add to that 100% of x ml or x ml acohol

The total alcohol concentration is 0.25(975 + x)

 

0.05(975) + x = 0.25(975 + x)

48.75 + x = 243.75 + .25x

.75x = 195

x = 260 ml of pure alcohol