Chemistry Problem: Calculating Molality of a Solution

What is the molality (in m) of a solution if 8.50 g of sodium chloride is dissolved in 50.0 mL of water at 20.2 oC?

Calculate the molality of the solution given the provided information.

Answer:

The molality of the solution is 2.92 m.

To calculate the molality of a solution, we need to follow several steps. First, convert the mass of sodium chloride to moles. The molar mass of sodium chloride (NaCl) is 58.44 g/mol. Dividing the mass of NaCl by its molar mass gives us 0.1456 mol.

Next, convert the volume of water to its mass using the density of water. The density of water at 20.2 oC is 0.998 g/mL. Multiplying the volume of water (50.0 mL) by its density gives us a mass of 49.9 g.

Finally, calculate the molality using the formula: molality (m) = moles of solute / mass of solvent (in kg). The mass of water in kg is 0.0499 kg. Dividing the moles of NaCl by the mass of water gives us a molality of 2.92 m.