500g urea aq. Sol. Has mole fraction 0.2 what is molality of sol.
answer to how much heat is required to raise the temperature of 68.0 g of AIF3 from 25 degrees celsius to 80.0 degrees celsius
Your question is answered above.
To find the molality of a solution, you need to know the amount of solute (in moles) and the mass of the solvent (in kilograms).
Let's start by determining the moles of urea in the solution.
1. Calculate the molar mass of urea (CO(NH2)2):
Molar mass of Carbon (C) = 12.01 g/mol
Molar mass of Oxygen (O) = 16.00 g/mol
Molar mass of Nitrogen (N) = 14.01 g/mol
Molar mass of Hydrogen (H) = 1.01 g/mol
Molar mass of urea (CO(NH2)2) = 12.01 + 16.00 + (2 * 14.01) + (4 * 1.01) = 60.06 g/mol
2. Calculate the moles of urea in the solution using the mole fraction:
Mole fraction = Moles of solute / (Moles of solute + Moles of solvent)
0.2 = Moles of urea / (Moles of urea + Moles of water)
Since water is commonly the solvent, let's assume the moles of water (solvent) are much higher than the moles of urea (solute). Therefore, the mole fraction of urea can be approximated to only the mole fraction of solute in this case:
0.2 = Moles of urea / Moles of urea
This implies that Moles of urea = 0.2
Now, to find the molality, you need the mass of the solvent (water) in kilograms. Unfortunately, we don't have that information in the given question. Without the mass of the solvent, it is not possible to calculate the molality. The molality depends on the mass of the solvent, not the solute.
The mass of the solution is 500. How much is urea and how much is water?
Let X = g urea
and 500-x = grams H2O
Then mols urea = X/60
mol H2O = (500-X/18)
Then
nurea/(nurea + nH2O) = 0.2
(X/60)/{[(X/60)] + [(500-X)/18]} = 0.2
I solved for X and obtained about 227 g for urea and 273 g H2O. You can work that out but that's very close to a mole fraction for urea of 0.2.
Then n urea = about 3.8
n H2O = about 15.2
From above we had 227 g urea (about 3.8 mols) and 273 g H2O
molality = (mols solute)/(kg solvent)
mols solute = about 3.8
kg solvent = about 0.273
m = ?
My numbers are estimates; you should recalculate each step.