The question, as presented, is incomplete. The entire question is shown below:

"<span>The density of a 13.2 mass % solution of NaF is 1.21 g/mL. Find the molarity of the solution."

We are asked to find the molarity of this solution, and molarity is defined as the amount of moles of a compound per unit volume, typically in units of mol/L.

The density of the NaF solution is 1.21 g/mL. Let's take a 1 L sample of this solution and determine the mass.

1.21 g/mL x 1000 mL = 1210 g of solution.

We are told that this solution is 13.2% NaF by mass. So the mass of NaF in this solution is:

1210 x 0.132 = 160 g NaF

We can then turn this mass of NaF into moles of NaF using the molecular weight of 42 g/mol.

160 g NaF / 42 g/mol = 3.80 moles NaF.

Now to convert this into molarity, we simply divide the amount of moles by the volume of sample, in this case 1L:

3.80 moles NaF/ 1L = 3.80 mol/L NaF or 3.80 M NaF.