Given:
mass of solute = 0.300 g
mass of solvent = 40.0 g = 0.0400 kg
[tex]K_{\text{b}} = \text{5.02°C/molal}[/tex]
[tex]\Delta T_{\text{b}} = \text{0.357°C}[/tex]
solute: unknown non-dissociating solute
solvent: CCl₄
Required:
molar mass of solute
Solution:
Step 1: Calculate the molality of solution.
[tex]\text{molality} = \frac{\Delta T_{\text{b}}}{K_{\text{b}}}[/tex]
[tex]\text{molality} = \frac{\text{0.357°C}}{\text{5.02°C/molal}}[/tex]
molality = 0.0711155 molal
Step 2: Calculate the number of moles of solute.
Note: 1 molal = 1 mol/kg
moles of solute = molality × mass of solvent
moles of solute = 0.0711155 mol/kg × 0.0400 kg
moles of solute = 0.00284462 mol
Step 3: Calculate the molar mass of solute.
[tex]\text{molar mass of solute} = \frac{\text{mass of solute}}{\text{moles of solute}}[/tex]
[tex]\text{molar mass of solute} = \frac{\text{0.300 g}}{\text{0.00284462 mol}}[/tex]
[tex]\boxed{\text{molar mass of solute = 105.5 g/mol}}[/tex]
[tex]\\[/tex]
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