80. What is the vapor pressure of a aqueous solution containing 10 % (by weight) ethylene glycol (62 g/mol) at 25 °C. PH2O = 24.3 torr at 25°C?
Let's call ethylene glycol ethg for this problem.
10% w/w ethg means 10 g ethg in 90 g H2O.
mols ethg = grams/molar mass = 10/62 = 0.16
mols H2O = 90/18 = 5
total mols = 5.16
Xethg = mols ethg/total mols = 0.16/5.16 =0.031
Psolution = Xsolute*Posolvent
Psolution = 0.031*24.3 = ?
Post your work if you get stuck.
To calculate the vapor pressure of the aqueous solution containing 10% ethylene glycol at 25 °C, we need to use Raoult's law. Raoult's law states that the vapor pressure of a solution is equal to the vapor pressure of the pure solvent multiplied by the mole fraction of the solvent in the solution.
First, we need to calculate the mole fraction of ethylene glycol in the solution. To do this, we need to consider the weight percent and the molar mass of ethylene glycol.
Given:
Weight percent of ethylene glycol = 10%
Molar mass of ethylene glycol = 62 g/mol
Step 1: Calculate the mass of ethylene glycol present in the solution.
Assuming we have 100 g of solution, the mass of ethylene glycol would be (10/100) * 100 g = 10 g.
Step 2: Convert the mass of ethylene glycol to moles.
Using the molar mass of ethylene glycol,
10 g ethylene glycol * (1 mol ethylene glycol/62 g ethylene glycol) = 0.161 mol ethylene glycol.
Step 3: Calculate the mole fraction of ethylene glycol.
The mole fraction of ethylene glycol (Xethylene glycol) is given by:
Xethylene glycol = moles of ethylene glycol / total moles in the solution
In this case, the total moles in the solution are the moles of water present, which we assume to be 100 g of water.
Using the molar mass of water (18 g/mol),
100 g water * (1 mol water/18 g water) = 5.556 mol water.
Now, we can calculate the mole fraction:
Xethylene glycol = 0.161 mol ethylene glycol / (0.161 mol ethylene glycol + 5.556 mol water)
Xethylene glycol ≈ 0.0284
Step 4: Calculate the vapor pressure of the solution.
We can use Raoult's law to calculate the vapor pressure.
vapor pressure of the solution (P solution) = mole fraction of ethylene glycol (Xethylene glycol) * vapor pressure of pure ethylene glycol (Pethylene glycol)
Given:
Vapor pressure of pure water (Pwater) = 24.3 torr
Using Raoult's law:
P solution = Xethylene glycol * Pethylene glycol
Since the vapor pressure of pure ethylene glycol is not provided, we cannot perform the final calculation.