The molal boiling-point elevation constant of water is $K_b = 0.52$ K kg/mol. What is the boiling point of a solution of $0.5$ mol of glucose in $500$ g of water? (Boiling point of pure water = $373$ K)
A$373.26$ K
B$373.00$ K
C$374.04$ K
D$373.52$ K
Answer & Solution
Correct answer: D. $373.52$ K
Molality $m = \dfrac{\text{moles of solute}}{\text{kg of solvent}} = \dfrac{0.5}{0.5} = 1$ mol/kg.
Elevation: $\Delta T_b = K_b \cdot m = 0.52 \times 1 = 0.52$ K.
New boiling point: $373 + 0.52 = 373.52$ K.
Glucose is a non-electrolyte (van't Hoff factor $i \approx 1$), so no correction is needed. For NaCl with the same molality, $\Delta T_b$ would roughly double.
Related questions
The mass of NaOH (M = 40 g/mol) required to prepare 500 mL of a 0.20 M NaOH solution isWhich of these solutions will boil at the highest temperature at 1 atm?The molality of a 1 M aqueous NaCl solution (density = 1.04 g/mL, NaCl M = 58.5 g/mol) is Osmotic pressure π of a dilute solution obeys π = C R T. Here C representsVan't Hoff factor i > 1 for a solute indicatesA negative deviation from Raoult law is expected whenIf a solute dimerises in solution, its observed molar mass compared with the calculated vaWhich of the following is NOT a colligative property?