How would you prepare a 25.0% water in ethyl alcohol solution using 100.0 ml of ethyl alcohol (The density of ethyl alcohol is 0.7893 g/ml)
Is that 25.0% w/w H2O in ethanol? I will assume so.
Assuming water and alcohol volumes are additive (actually they do not)
100 mL ethanol has a mass of m = v*d = 100 x 0.789 = 78.9g ethanol.
Since % is g/100 g soln, that will be
(x/78.9 EtOH + 21.1 H2O) = 0.25
Therefore, x = 0.25g H2O.
We mix 0.25g H2O in 100 mL H2O and we will have 25%.
[0.25g H2O/(100 g soln)]*100 = 25% w/w.
To prepare a 25.0% water in ethyl alcohol solution, you need to determine how much water and ethyl alcohol are required.
Step 1: Calculate the amount of ethyl alcohol needed
Since the total volume of the solution is 100.0 ml, the volume of ethyl alcohol should be 75.0 ml to make up 75% of the solution (since 100% - 25% = 75%).
Step 2: Convert the volume of ethyl alcohol to mass
To convert the volume of ethyl alcohol to mass, you need to know its density. Given that the density of ethyl alcohol is 0.7893 g/ml:
Mass of ethyl alcohol = Volume of ethyl alcohol x Density of ethyl alcohol
Mass of ethyl alcohol = 75.0 ml x 0.7893 g/ml
Step 3: Calculate the amount of water needed
To determine the amount of water required to make up the remaining 25% of the solution, subtract the volume of ethyl alcohol from the total volume of the solution:
Volume of water = Total volume of solution - Volume of ethyl alcohol
Volume of water = 100.0 ml - 75.0 ml
Step 4: Convert the volume of water to mass
Since the density of water is 1 g/ml, the volume of water directly gives the mass:
Mass of water = Volume of water
Now you know the amount of ethyl alcohol and water needed to prepare the solution.