The boiling point of pure acetic acid (C₂H₄O₂) is 117.90 ° C. A solution of 1.80 g of glucose (molar mass = 180 g/mol) dissolved in 25.0 g acetic acid was found to boil at 119.13 ° C. The value of k_bfor acetic acid (in units of ° C/molal) is:

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The boiling point elevation ($\Delta T_b$) can be calculated using the formula $\Delta T_b = i \cdot K_b \cdot m$, where $i$ is the van't Hoff factor (which is 1 for glucose, a non-electrolyte), $K_b$ is the ebullioscopic constant of the solvent (acetic acid in this case), and $m$ is the molality of the solution. Given the boiling point elevation ($119.13 °C - 117.90 °C = 1.23 °C$), and the molality ($\frac{1.80 \, \text{g} / 180 \, \text{g/mol}}{25.0 \, \text{g} / 1000 \, \text{g/kg}} = 0.4 \, \text{mol/kg}$), we can solve for $K_b$. Rearranging the formula gives $K_b = \frac{\Delta T_b}{i \cdot m} = \frac{1.23 °C}{1 \cdot 0.4 \, \text{mol/kg}} = 3.08 °C/\text{molal}$.

The Boiling Point of Pure Acetic Acid (C2H4O2) Is 117

The Boiling Point of Pure Acetic Acid (C₂H₄O₂) Is 117