A concentrated ammonia solution is 28.0% NH₃ by mass and has a density of 0.939 g/mL at 25°C.The remainder of material is solvent.What is the molality of NH₃ in the solution? A)22.8 m B)16.4 m C)12.8 m D)437 m E)0.236 m

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Quizplus · Accepted Answer

The molality (m) of a solution is defined as the number of moles of solute per kilogram of solvent. To find the molality of NH3 in the solution, we first calculate the mass of NH3 in 1000 g of solution, then find the moles of NH3, and finally calculate the molality.Given that the solution is 28.0% NH3 by mass, this means there are 280 g of NH3 in 1000 g of solution. The molar mass of NH3 is approximately 17.03 g/mol, so the number of moles of NH3 in 280 g is 280 g / 17.03 g/mol ≈ 16.44 moles.The mass of the solvent (water) in 1000 g of solution is 1000 g - 280 g = 720 g = 0.720 kg.Therefore, the molality (m) of the solution is the number of moles of NH3 per kilogram of solvent, which is 16.44 moles / 0.720 kg ≈ 22.8 m.

A Concentrated Ammonia Solution Is 28