Question

What is the percent concentration of a 6m solution of NaCl?

Answer 1

A 6 mol/L solution is 30 % by mass.

Percent by mass = `"Mass of NaCl"/"Total mass of solution"` × 100 %

Let's assume that we have 1 L of the solution.

Calculate Mass of NaCl

Mass of NaCl = 1 L soln × `(6" mol NaCl")/(1" L soln") × (58.44" g NaCl")/(1" mol NaCl")` = 400 g NaCl.

Calculate Mass of Solution

To get the mass of the solution, we must know its density. I will assume that density = 1.2 g/mL.

Mass of solution = 1000 mL × `(1.2" g")/(1" mL")` = 1200 g

Calculate Percent by Mass

Percent by mass = `"Mass of NaCl"/"Total mass of solution" × 100 % = (400" g")/(1200" g")` × 100 % = 30 %

Note: I have calculated the answer to only 1 significant figure, because that is all you gave me for the molarity of the NaCl. If you need more precision, you will have to recalculate.