Question

Doc Inmaking does a titration using sodium hydroxide (NaOH) and sulfuric acid (H2SO4). He pipets 20.00 mL of H2SO4 solution into the Erlenmeyer flask and adds two drops of phenolphthalein. He does the titration using 0.5000 M NaOH. The initial buret reading is 0.70 mL and the final buret reading is 35.23 mL. Write the balanced chemical equation for sodium hydroxide reacting with sulfuric acid to produce sodium sulfate and water. Determine the mole ratio between the acid and the base. (Hint: it is not one-to-one.) Then calculate the molarity of the sulfuric acid (H2SO4) solution. Enter the H2SO4 concentration with 4 significant digits and units of mol/L.

Answer 1

The initial buret reading is 0.70 mL

The final buret reading is 35.23 mL

The volume of NaOH   = The final buret reading-The initial buret reading

                                     = 35.23-0.70   = 34.53ml

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

   1 mole       2 moles

H2So4: NaOH   = 1:2

   H2So4                                                          NaOH

M1 =                                                          M2 = 0.5M

V1    = 20ml                                                 V2 = 34.53ml

n1 = 1                                                          n2 = 2

               M1V1/n1     =      M2V2/n2

                 M1             =      M2V2n1/V1n2

                                   = 0.5*34.53*1/20*2    = 0.4316M

molarity of H2SO4 = 0.4316M