Question

A student weighs out a 0.761 g sample of NaF, transfers it to a 125 ml volumetric flask, adds enough water to dissolve it and then adds water to the 125 mL tick mark. What is the molarity of sodium fluoride in the resulting solution?

A) Molarity = 0.761 M
B) Molarity = 0.7610 M
C) Molarity = 6.09 M
D) Molarity = 6.09 × 10^3 M

Answer 1

The molarity of the resulting NaF solution is 0.145 M.

Step-by-step explanation:

To determine the molarity of the sodium fluoride (NaF) solution, we need to calculate the amount of NaF added. The student weighed out a 0.761 g sample of NaF. Since the molar mass of NaF is 41.99 g/mol, the number of moles in the sample is 0.761 g / 41.99 g/mol = 0.0181 mol.

The student then transferred the NaF to a 125 ml volumetric flask and added enough water to dissolve it and reach the 125 mL mark. Thus, the final volume of the solution is 125 mL = 0.125 L.

To calculate the molarity, we divide the number of moles by the volume in liters. Molarity (M) = moles/volume = 0.0181 mol / 0.125 L = 0.145 M.