Calculating ion molarity using solute mass

Question

A chemist prepares a solution of sodium chloride (NaCl) by measuring out 55.5 mg of NaCl into a 100. mL volumetric flask and filling to the mark with distilled water.

calculate the molarity of Cl anions in the chemist’s solution

be sure your answer is rounded to 3 SF

Answer 1

moles of NaCl = mass/molar mass = (55 x 10^-3 g)/58.5 g/mol = 9.402 x 10^-4 mol

Concentration = moles/volume in litres= 9.402 x 10^-4 mol/0.1L = 9.402 x 10^-3 M NaCl

Since 1 mole of NaCl produces 1 mole of Cl^- ions, so concentration of Cl^- ions = 9.402 x 10^-3 M