Question

The sterile saline solution used to rinse contact lenses can be made by dissolving 400 mg of nacl in sterile water and diluting to 100 ml. what is the molarity of the solution?

Answer 1

.068443 mol/L First we must find the molar mass of NaCl. We find the atomic mass of sodium and chlorine and add them: Na: 22.9898 Cl: 35.453 22.9898 + 35.453 = 58.4428g/mol The we find the number of mols contained in 400mg of NaCl: .4g / 58.4428g/mol .0068443 mol Since 100mL is a tenth of a liter we can multiple the number of mols by ten: .068443 mol/L