What is the molality of a 30.0% by mass hydrochloric acid solution? The density of the solution is 1.1493 g/mL.
A)0.0344 m
B)11.7 m
C)0.377 m
D)9.29 m
E)9.45 m

Question

Quizplus · Accepted Answer

Molality (m) is defined as the number of moles of solute per kilogram of solvent. To find the molality of the hydrochloric acid solution, we first need to calculate the moles of HCl in 1000 g of the solution and the mass of the solvent (water) in kilograms.Given that the solution is 30.0% HCl by mass, this means that in 1000 g of the solution, there are 300 g of HCl and 700 g of water (since 1000 g - 300 g = 700 g).The molar mass of HCl is approximately 36.46 g/mol, so the moles of HCl in 300 g are calculated as follows:$$ \text{Moles of HCl} = \frac{300 \, \text{g}}{36.46 \, \text{g/mol}} \approx 8.23 \, \text{mol} $$The mass of the solvent (water) in kilograms is:$$ 700 \, \text{g} = 0.7 \, \text{kg} $$Finally, the molality (m) is calculated as:$$ m = \frac{\text{Moles of solute}}{\text{Kilograms of solvent}} = \frac{8.23 \, \text{mol}}{0.7 \, \text{kg}} \approx 11.7 \, \text{m} $$Therefore, the correct answer is 11.7 m, which corresponds to choice B.

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