A. 6.50%
B. 0.0204
C. 1.101 M
D. 1.157 mol/kg
Step-by-step explanation:
To calculate the concentration of urea in various units, we first need to find the molecular weight of urea and the total mass of the solution.
The molecular weight of urea (NH2)2CO:
N = 14.01 g/mol, H = 1.01 g/mol, C = 12.01 g/mol, O = 16.00 g/mol
(2 * (1 * 14.01 + 2 * 1.01)) + 12.01 + 16.00 = 60.06 g/mol
a) Weight-percent:
Weight-percent = (mass of solute / total mass of solution) x 100
Total mass of solution = mass of solute (urea) + mass of solvent (water) = 66.0 g + 950 g = 1016 g
Weight-percent = (66.0 g / 1016 g) x 100 ≈ 6.50%
b) Mole fraction:
Moles of urea = mass of urea / molecular weight of urea = 66.0 g / 60.06 g/mol ≈ 1.099 mol
Moles of water = mass of water / molecular weight of water = 950 g / 18.01 g/mol ≈ 52.75 mol
Mole fraction of urea = moles of urea / (moles of urea + moles of water) = 1.099 mol / (1.099 mol + 52.75 mol) ≈ 0.0204
c) Molarity:
Volume of solution = mass of solution / density = 1016 g / 1.018 g/mL ≈ 998.04 mL ≈ 0.99804 L
Molarity = moles of urea / volume of solution in liters = 1.099 mol / 0.99804 L ≈ 1.101 M
d) Molality:
Molality = moles of solute / mass of solvent in kg = 1.099 mol / 0.95 kg ≈ 1.157 mol/kg