Question

a pharmacist needs to strengthen a 15% alcohol solution to one of 32% alcohol how much pure alcohol should be added to 800 ml of 15% solution​

Answer 1

Answer:

200 ml

Step-by-step explanation:

In 800 ml of 15% solution, since 100% - 15% = 85%, the amount of water is:

water volume = 85% of 800 ml = 0.85 × 800 ml = 680 ml.

Let V be the volume of 32% solution after adding pure alcohol.

The amount of water is the same (i.e. we're adding pure alcohol), and as a proportion, it is 100% - 32% = 68%.  So...

68% of V = 680 ml

=> 0.68 V = 680 ml

=> V = 680/0.68 ml = 1000 ml

So the volume of the 32% solution will be 1000 ml.

The amount of pure alcohol to add is then 1000 ml - 800 ml = 200 ml.