Question

Calculate the molarity of sodium sulfate in a solution prepared by mixing 45.0 mL of 0.15 M sulfuric acid with 15.0 mL of 0.850M sodium hydroxide.

Answer 1

H2SO4 millimoles = 45 x 0.15 = 6.75

NaOH millimoles = 12.75

H2SO4 + 2 NaOH ----------------------> Na2SO4 + 2H2O

1                2                                            1                  1

6.75           12.75                                    ?                   ?

here limiting reagent is NaOH

so 2 millimoles NaOH gives 1 millimole Na2SO4

12.75 millimole NaOH gives   howmany millimoles Na2SO4

Na2SO4 millimoles = 12.75 /2 = 6.375

Na2SO4 molarity = millimoles / total volume

                            = 6.375 / 15 + 45

                            = 0.106 M