the concentration of urea (MW=60.0g/mol) in a solution prepared by dissolving 23g of urea in 64g of H2O is ____ molal
molal means moles of solute per kg of solvent
moles of urea ... (mass of urea) / (molar mass of urea)
kg of H2O ... (mass of H2O) / (1000 g / kg)
To find the concentration of urea in the given solution, we need to calculate the molality.
Molality (m) is a measure of the number of moles of solute (urea) dissolved per kilogram of solvent (H2O). It can be calculated using the following formula:
Molality (m) = (Number of moles of solute) / (Mass of solvent in kg)
Step 1: Calculate the number of moles of urea:
Number of moles of urea = Mass of urea / Molecular weight of urea
Given: Mass of urea = 23g
Molecular weight of urea = 60.0 g/mol
Number of moles of urea = 23g / 60.0 g/mol
Step 2: Calculate the mass of the solvent (H2O) in kg:
Mass of H2O = 64g
Convert mass of H2O to kg: 64g / 1000g/kg
Step 3: Calculate the molality:
Molality (m) = (Number of moles of urea) / (Mass of H2O in kg)
Now, let's perform the calculations:
Number of moles of urea = 23g / 60.0 g/mol = 0.3833 mol
Mass of H2O in kg = 64g / 1000g/kg = 0.064 kg
Molality (m) = 0.3833 mol / 0.064 kg
Molality (m) ≈ 5.995 mol/kg
Therefore, the concentration of urea in the given solution is approximately 5.995 molal.