Explain how you can prepare 75% Ethanol

Answer 1

It depends on concentration of ethanol you are using and what volume you are making.

For the purpose of an example, I will assume a stock solution of 95% ethanol solution and you need 500 mL of the 75% Ethanol solution.

We will use the following equation where C₁ and C₂ refer to the initial and final concentrations of the solutions, respectively, and V₁ and V₂ refer to the volumes of the solutions, respectively.

C₁V₁ = C₂V₂

Substitute in what you know:

C₁ = 0.95 C₂ = 0.75

V₁ = x V_{2 =} 500 mL

The equation becomes:

x = 0.75 x 500 = 394 mL

0.95

In this example, you would need to add 394 mL of the stock solution of 95% ethanol to 106 ml of water.

Using the above equation and and whatever initial concentration of alcohol you have available will get you any volume you need. Hope this helps!