A solution is made by mixing 25.0 g of NaOH in H₂O. What is the amount of H₂O in the solution? (Mole fraction of solute = 0.090; molar mass of NaOH = 40.0 g/mol; molar mass of H₂O = 18.0 g/mol)

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Quizplus · Accepted Answer

The mole fraction of NaOH (solute) is given as 0.090. The mole fraction of solvent (H₂O, which seems to be a placeholder for water, H2O) is therefore 1 - 0.090 = 0.910. The moles of NaOH are calculated as 25.0 g / 40.0 g/mol = 0.625 moles. Using the mole fraction formula, $x_{solvent} = \frac{n_{solvent}}{n_{solvent} + n_{solute}}$, and rearranging for $n_{solvent}$, we get $n_{solvent} = \frac{x_{solvent} \times n_{solute}}{1 - x_{solvent}}$. Substituting the values, $n_{solvent} = \frac{0.910 \times 0.625}{1 - 0.910} = \frac{0.56875}{0.090} = 6.31944$ moles of solvent. The mass of the solvent (water) is then $6.31944 \times 18.0 g/mol = 113.75 g$, which rounds to 113.8 g.

A Solution Is Made by Mixing 25