Question

If 750 mL of 0.50 mol/L sodium chloride solution is uncovered on a windowsill and 150 mL of the solvent evaporates, what will the new concentration of the sodium chloride solution be?

Answer 1

A way of solving this question is using the molarity formula and finding the number of moles present in the solution, the molarity formula is:

M = n/V

where:

M = molar concentration in mol/L

n = number of moles

V = volume in liters

Now let's add the values to the formula

0.50 = n/0.750 L

n = 0.375 moles

Now let's use the molarity formula again, but with the new volume (750 mL - 150 mL = 600 mL)

M = 0.375/0.600

M = 0.625 mol/L, this is the new concentration of NaCl