a) Biphenyl, C12H10, is a nonvolatile, nonionizing solute that is soluble in benzene, C6H6. At 25 degrees Celcius, the vapor pressure of pure benzene is 100.84 torr. What is the vapor pressure of a solution made from dissolving 13.8 g of biphenyl in 32 g of benzene?

b) Express the concentration of a 0.07 M aqueous solution in fluoride, F^-, in mass parts per million. Assume the density of the solution is 1.00 g/mL.

Note the correct spelling of celsius.

psoln = Xbenzene*Pobenzene

You need Xbenzene. Get that from
nbiphenyl = grams/molar mass = ?
nbenzene = grams/molar mass = ?

Xbenzene = nbenzene/total mols.
Then substitute Xbenzene in first equation above and solve for p solution.

a) To calculate the vapor pressure of a solution, you can use Raoult's Law, which states that the vapor pressure of a solution is equal to the mole fraction of the solvent multiplied by the vapor pressure of the pure solvent.

First, calculate the number of moles of each component:
- For biphenyl: The molar mass of biphenyl is 154.21 g/mol. Therefore, the number of moles of biphenyl is 13.8 g / 154.21 g/mol = 0.0895 mol.
- For benzene: The molar mass of benzene is 78.11 g/mol. Therefore, the number of moles of benzene is 32 g / 78.11 g/mol = 0.4099 mol.

Next, calculate the mole fraction of benzene (solvent) in the solution:
Mole fraction of benzene = moles of benzene / total moles
Mole fraction of benzene = 0.4099 mol / (0.0895 mol + 0.4099 mol) = 0.820

Now, we can use Raoult's Law to calculate the vapor pressure of the solution:
Vapor pressure of solution = mole fraction of benzene * vapor pressure of pure benzene
Vapor pressure of solution = 0.820 * 100.84 torr = 82.87 torr

Therefore, the vapor pressure of the solution made from dissolving 13.8 g of biphenyl in 32 g of benzene is 82.87 torr.

b) To express the concentration in mass parts per million (ppm), you need to convert the molar concentration to mass concentration.

First, calculate the mass of fluoride (F^-) in the solution:
Mass of fluoride = molar concentration * volume * molar mass
Assuming a volume of 1 L (as the density is given in g/mL), the mass of fluoride in the 0.07 M solution is:
Mass of fluoride = 0.07 mol/L * 1 L * (18.998 g/mol) = 1.3299 g

Next, convert the mass of fluoride to mass parts per million (ppm):
Mass parts per million = (mass of fluoride / total mass of solution) * 1,000,000
The total mass of the solution is equal to the density (1.00 g/mL) multiplied by the volume (1 L):
Total mass of solution = 1.00 g/mL * 1 L = 1000 g

Mass parts per million = (1.3299 g / 1000 g) * 1,000,000 = 1329.9 ppm

Therefore, the concentration of the 0.07 M aqueous solution in fluoride, F^-, can be expressed as 1329.9 ppm.