A bottle of win contains 12.5% ethanol by volume. The density of ethanol (C2H5OH) is .79 g/mL. Calculate the concentration of ethanol in wine as mass percent and molality.

I calculated molality as 2.4 m/kg, but I'm stumped on the mass percent [although I'm hitting the right area.] Is the solvent water?

I calculated the molality as 2.45 mols/kg solvent so I assume you are doing that part correctly.

For percent by mass.
12.5 v/v percent is
12.5 mL EtOH in (12.5 mL EtOH + 87.5 mL H2O).
12.5 mL with density of 0.79 g/mL = 9.875 g.
mass %= [mass EtOH/(mass EtOH + mass H2O)]x 100 =
[9.875g/(9.875 g + 87.5 g)]x100 = 10.14 w/w percent.
Check my thinking. Check my arithmetic.

It comes out to be 10.2. Check your math and do it over again. Your very close to the answer

Yes, you are correct in assuming that the solvent in this case is water.

To calculate the mass percent of ethanol in wine, we need to find the mass of ethanol and the mass of the total solution (ethanol + water).

Given that the density of ethanol is 0.79 g/mL and the wine contains 12.5% ethanol by volume, we can calculate the mass of ethanol as follows:

Mass of ethanol = volume of ethanol * density of ethanol
= 12.5 mL * 0.79 g/mL
= 9.875 g

To calculate the mass of the total solution, we need to consider that the volume of the solution is equal to the sum of the volumes of ethanol and water. Since the volume percent of ethanol is 12.5%, the volume percent of water would be 100% - 12.5% = 87.5%. Therefore, the volume of water is 87.5 mL.

Mass of water = volume of water * density of water
= 87.5 mL * 1 g/mL (density of water is approximately 1 g/mL)
= 87.5 g

Now, we can calculate the mass percent of ethanol in wine as follows:

Mass percent of ethanol = (Mass of ethanol / (Mass of ethanol + Mass of water)) * 100
= (9.875 g / (9.875 g + 87.5 g)) * 100
= 10.14%

Therefore, the mass percent of ethanol in wine is approximately 10.14%.

It seems like you are hitting the right area, but do double-check your calculations to ensure accuracy.

The first step is to calculate the molality correctly, which you have done correctly, obtaining a value of 2.45 mol/kg solvent.

Now let's calculate the concentration of ethanol in wine as a mass percent:

To do this, we need to find the mass of ethanol and the mass of the total solution (ethanol + water).

Given that the density of ethanol is 0.79 g/mL, we can calculate the mass of ethanol in the wine using the volume percentage given (12.5%):
Volume of ethanol = 12.5 mL
Mass of ethanol = Volume of ethanol x Density of ethanol
Mass of ethanol = 12.5 mL x 0.79 g/mL = 9.875 g

The total volume of the solution is the sum of the volume of ethanol and the volume of water. Since the volume percentage given is for ethanol, we can assume the remaining part of the solution is water. Therefore:
Volume of water = 100 mL - 12.5 mL = 87.5 mL

Now, let's calculate the mass percent:
Mass percent = (Mass of ethanol / Mass of solution) x 100

Mass of solution = Mass of ethanol + Mass of water
Mass of solution = 9.875 g + 87.5 g = 97.375 g

Mass percent = (9.875 g / 97.375 g) x 100 = 10.14%

So, the concentration of ethanol in wine as a mass percent is approximately 10.14%.

Regarding the solvent, yes, in this case, the solvent is considered to be water.