At 20 degrees C ethanol has a density of 0.789 g/ml and H2O has a density of 1.0 g/ml. What is the % by volume of ethanol of a solution made by adding 50g of ethanol with 50g of H2O?

Use density = mass x volume to convert 50 g ethanol to volume and to convert 50.0 g H2O to volume.

%ethanol v/v = (volume ethanol/total volume)*100 = ?

i thought that density = m/v?

i've done the math and i think you are right because based on the above formula my answer is 126.74%
However, i don't understand why if the density formula is as you stated?

1/50 = .02, 1/.789 = .01578

(0.01578/0.02) x 100 = 78.9%

To find the percent by volume of ethanol in the solution, we need to determine the volume of ethanol and water added.

First, we need to convert the mass of ethanol and water into volume using their respective densities.

The density of ethanol is given as 0.789 g/ml. Therefore, the volume of ethanol can be calculated as follows:

Volume of ethanol = mass of ethanol / density of ethanol
Volume of ethanol = 50g / 0.789 g/ml

Calculating the above equation, we find:
Volume of ethanol = 63.39 ml

Similarly, the volume of water can be calculated using its density, which is given as 1.0 g/ml:

Volume of water = mass of water / density of water
Volume of water = 50g / 1.0 g/ml

Calculating the above equation, we find:
Volume of water = 50 ml

Now, to find the percent by volume of ethanol in the solution, we need to calculate the total volume of the solution, which is the sum of the volumes of ethanol and water:

Total volume of solution = volume of ethanol + volume of water
Total volume of solution = 63.39 ml + 50 ml
Total volume of solution = 113.39 ml

Finally, we can calculate the percent by volume of ethanol using the following formula:

Percent by volume of ethanol = (volume of ethanol / total volume of solution) x 100
Percent by volume of ethanol = (63.39 ml / 113.39 ml) x 100

Calculating the above equation, we find:
Percent by volume of ethanol = 55.9%

Therefore, the % by volume of ethanol in the solution made by adding 50g of ethanol with 50g of H2O is approximately 55.9%.