The mole fraction of ethanol () in an aqueous ethanol-water binary mixture is determined to be exact — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question

💡 Solution & Explanation

Step 1: Assume a total of $1.0\text{ mole}$ of the mixture. Moles of ethanol = $0.25\text{ mol}$. Moles of water = $1.00 - 0.25 = 0.75\text{ mol}$. Step 2: Convert moles to absolute mass. Mass of ethanol = $0.25\text{ mol} \times 46\text{ g/mol} = 11.5\text{ g}$. Mass of water = $0.75\text{ mol} \times 18\text{ g/mol} = 13.5\text{ g}$. Total mass of mixture = $11.5 + 13.5 = 25.0\text{ g}$. Step 3: Calculate mass percentage. % w/w of ethanol = $\left(\frac{11.5}{25.0}\right) \times 100 = 46\%$.