the concentration of urea (MW=60.0g/mol) in a soltuion prepared by dissolving 16g of urea in 39g of H2O is ____ molal
moles of urea:16(g)/60(g/mol)=0.267(mol)
39(g)*1(kg)/1000(g)=0.039kg
m=0.267/0.039=6.846(mol/kg)
mols urea = grams/molar mass
m = mols/kg solvent = mols/0.039 = ?
7
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To find the concentration of urea in a solution in molal units, we need to calculate the moles of urea and the mass of the solvent, in this case, water.
First, let's calculate the moles of urea. We can use the formula:
moles = mass / molecular weight
The mass of urea is given as 16 g, and the molecular weight of urea is 60.0 g/mol. Substituting these values, we can calculate the moles of urea:
moles of urea = 16 g / 60.0 g/mol
moles of urea ≈ 0.267 mol
Next, we need to determine the mass of the solvent, which is water. The mass of water is given as 39 g.
Now, we can calculate the molality (molal concentration) of urea in the solution using the formula:
molality = moles of solute / mass of solvent (in kg)
To convert the mass of the solvent (water) to kg, we divide by 1000:
mass of solvent (water) = 39 g / 1000 = 0.039 kg
Finally, substituting the values in the formula, we can calculate the molality:
molality = 0.267 mol / 0.039 kg
molality ≈ 6.85 mol/kg
Therefore, the concentration of urea in the solution is approximately 6.85 molal.