You need to make 350mls of a 70% ethanol solution of EtOH from a 95% solution. How would you do this?

Assume the 95 percent solution is made of 20 parts, one of which is water. The 70 percent will have six parts water. So add five parts water to the 95 percent, and you have it.

So you have 20 parts + 5 parts=350ml
25 parts= 350ml
1 part= 350/25 ml

So take five parts (5*350/25 ml) water, and the remaining 95 percent EtOH to the 350ml mark. If you don't have a mark,then add 350- 5*350/25 ml of EtOH.

check my thinking.

To make 350ml of a 70% ethanol solution from a 95% ethanol solution, you will need to calculate the amount of the 95% solution and the amount of water to mix together.

Let's assume x is the volume of the 95% ethanol solution needed.

First, let's determine the amount of ethanol in the 95% solution by using the percentage composition formula:

Ethanol amount = (Percentage of ethanol / 100) * Solution volume
Ethanol amount in the 95% solution = (95 / 100) * x = 0.95x

Next, let's determine the amount of water needed in the final solution:

Water amount = Total solution volume - Ethanol amount
Water amount = 350ml - 0.95x

Now, let's set up an equation to find the value of x.

Ethanol amount in the final solution = Ethanol amount in the 95% solution + Ethanol amount in the water

(0.70) * 350ml = 0.95x + (350ml - 0.95x)

Simplifying the equation:

245ml = 0.95x + 350ml - 0.95x
245ml - 350ml = -0.95x + 0.95x
-105ml = 0

We can see that the equation is inconsistent and cannot be solved. It means it is not possible to create a 70% ethanol solution with the given 95% ethanol solution and water.

Hence, to make 350ml of a 70% ethanol solution, you will need ethanol of a higher concentration or an alternative ethanol source with a higher percentage of ethanol.