What is the ionic molality of sodium ions in a solution of 25.7 g NaNO 3 dissolved in enough water to make a 150.0 mL of solution? Density of the solution is 1.02 g/mL.

What is the ionic molality of sodium ions in a solution that's 25.7 grams of sodium nitrate dissolved in enough water to make a 150 ml's of solution. We're also told that the density of the solution is 1.02 grams per milliliter. Alright. So we need the ionic molality of sodium ion or osmolality of sodium ions. So we're gonna say osmolality equals the number of ions, which in this case is the ions of sodium. So this breaks up into 1 sodium ion and 1 nitrate ion. So number of ions is just equal to 1 times, we need the molality of the solution. So remember, molality equals the moles of solute, so that would be moles of sodium nitrate, divided by kilograms of our solvent, which would be the water. So we have 25.7 grams of sodium nitrate. We're gonna say 1 mole of sodium nitrate is composed of 1 sodium, 1 nitrogen, and 3 oxygens. The combined mass is 20 85 grams. Okay. So here that comes out to be 0.30235 moles. So that's my moles of sodium nitrate. Now we need to determine the kilograms of my water. Well, we're told the volume of the solution is 150 ml, and we're told the density of the solution. So we're gonna use those 2 together to to help us find out the total mass of our solution. So that comes out to be 153 grams of solution. If I subtract out of this 25.7 grams of my solute, then the difference will equal my grams of solvent. So that's 127.3 grams of solvent, which is the water. So we change that into kilograms, which is 0.1273 kilograms of water. And when we do that, it equals 2.375 mobile. Okay? And based on sig figs and the best possible answer, the best answer here will be option d, 2.37. Okay? Technically, when you round up it would be 2.38, but here we want the best possible answer, which is, 2.37 mole. So here that would mean that option d is the correct answer.

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14. Solutions

Molality

General Chemistry

14. Solutions

Molality

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Multiple Choice

What is the ionic molality of sodium ions in a solution of 25.7 g NaNO₃ dissolved in enough water to make a 150.0 mL of solution? Density of the solution is 1.02 g/mL.

1.98 m

2.57 m

4.74 m

2.37 m

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Verified step by step guidance

Calculate the molar mass of NaNO3 by adding the atomic masses of sodium (Na), nitrogen (N), and three oxygens (O).

Convert the mass of NaNO3 (25.7 g) to moles using the formula: moles = mass / molar mass.

Determine the mass of the solution using its volume (150.0 mL) and density (1.02 g/mL) with the formula: mass = volume × density.

Calculate the mass of the solvent (water) by subtracting the mass of NaNO3 from the total mass of the solution.

Find the molality of sodium ions by dividing the moles of NaNO3 by the mass of the solvent in kilograms, using the formula: molality (m) = moles of solute / mass of solvent (kg).