Question

What is the molarity of 109mL of a 17.2% NaCl solution?

Answer 1

1.7% (w/v) solution of NaCl solution means that there is 17.2 g NaCl in 100 mL solution.

So, amount of NaCl is 109 mL solution = (17.2 g / 100 mL) x 109 mL

                                                            = 18.748 gram

Number of moles of NaCl in 18.748 g sample = mass of NaCl / Molecular mass of NaCl

                                                            = 18.748 g / 58.44 g mol^-1

                                                            = 0.32081 moles

Molarity is defined as number of moles of solute in 1 L solution.

Or, Molarity, M = moles of solutes / volume in L

                        = 0.32081 moles / 0.109 L                      [1 L = 1000 mL; so, 109 mL = 0.109 L]

                        = 2.94

Hence, molarity of NaCl solution = 2.94 M