Question

what is the mass % of ethylene glycol in a 2.33 m solution of ethylene glycol (molar mass = 62.07 g/mol) in water? the density of the solution is 1.07 g/ml.

Explanation:

Step1: Assume 1L of solution

Volume of solution: $V = 1000\ \text{mL}$

Step2: Calculate moles of ethylene glycol

Moles = Molarity × Volume
$n = 2.33\ \text{mol/L} \times 1\ \text{L} = 2.33\ \text{mol}$

Step3: Calculate mass of ethylene glycol

Mass = Moles × Molar mass
$m_{\text{glycol}} = 2.33\ \text{mol} \times 62.07\ \text{g/mol} = 144.6231\ \text{g}$

Step4: Calculate total mass of solution

Mass = Density × Volume
$m_{\text{solution}} = 1.07\ \text{g/mL} \times 1000\ \text{mL} = 1070\ \text{g}$

Step5: Calculate mass percentage

Mass % = $\frac{\text{Mass of solute}}{\text{Mass of solution}} \times 100\%$
$\text{Mass \%} = \frac{144.6231\ \text{g}}{1070\ \text{g}} \times 100\%$

Answer:

13.5% (rounded to three significant figures)