QuestionApril 24, 2025

What is the concentration in molarity of an aqueous solution which contains 20.01% by mass acetonitrile (MM=41.05g/mol) ? The density of the solution is 0.8100g/mL

What is the concentration in molarity of an aqueous solution which contains 20.01% by mass acetonitrile (MM=41.05g/mol) ? The density of the solution is 0.8100g/mL
What is the concentration in molarity of an aqueous solution which
contains 20.01%  by mass acetonitrile (MM=41.05g/mol) ? The density
of the solution is 0.8100g/mL

Solution
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Answer

3.947 M Explanation 1. Calculate mass of acetonitrile Assume 100 g of solution. Mass of acetonitrile = 20.01\% \times 100 = 20.01 g. 2. Calculate moles of acetonitrile Moles = \frac{20.01 \text{ g}}{41.05 \text{ g/mol}} = 0.4873 mol. 3. Calculate volume of solution Volume = \frac{100 \text{ g}}{0.8100 \text{ g/mL}} = 123.46 mL = 0.12346 L. 4. Calculate molarity Molarity = \frac{0.4873 \text{ mol}}{0.12346 \text{ L}} = 3.947 M.

Explanation

1. Calculate mass of acetonitrile<br /> Assume 100 g of solution. Mass of acetonitrile = $20.01\% \times 100 = 20.01$ g.<br />2. Calculate moles of acetonitrile<br /> Moles = $\frac{20.01 \text{ g}}{41.05 \text{ g/mol}} = 0.4873$ mol.<br />3. Calculate volume of solution<br /> Volume = $\frac{100 \text{ g}}{0.8100 \text{ g/mL}} = 123.46$ mL = $0.12346$ L.<br />4. Calculate molarity<br /> Molarity = $\frac{0.4873 \text{ mol}}{0.12346 \text{ L}} = 3.947$ M.
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