Question

What is the percentage strength (v/v) of Diluted Alcohol, NF, which results from mixing 50 mL of Alcohol, USP (95.0%, v/v) with 50 mL of Purified Water, USP?

C1xV1 = C2xV2
95% x 50ml = C2 x 97ml
C2 = 49%

This was an example my professor put up. I can not comprehend why 97 ml is used as V2. Is it not 100ml when you are mixing 50ml of a solution with 50ml of water?

Answer 1

Nvm. Apparently when you mix water and alcohol theres a contraction effect that reduces the final vol by ~3%.

Answer 2

I seem to remember that 50 mL water + 50 mL ethyl alcohol gives 95 mL solution.