Question

You are given a sulfuric acid solution of unknown concentration. You dispense 10.00 mL of the unknown solution into an Erlenmeyer flask and add 12.20 mL of distilled water and a drop of phenopthalein to the flask. You fill your buret with 0.103 M NaOH (aq) solution and begin the titration. During the titration you rinse the tip and the sides of the Erlenmeyer flask with 3.52 mL of distilled water. It requires 10.38 mL of your NaOH (aq) solution to reach the endpoint and a very faint pink color in the flask.  

What is the concentration of your sulfuric acid solution in M (Remember the balanced equation for this reaction)?

Answer 1

The balanced equation is

H2SO4 + 2NaOH give Na2SO4 + H2O

The H2SO4 in the Erlenmeyer flask took 10.38 mL 0.103 M NaOH

number of moles of NaOH present in this volume = (0.103/1000) x10.38 = 0.0010 moles

Since one mole NaOH reacts with 0.5 H2SO4, the number of moles of H2SO4 = 0.0005 moles

(Since we dealing with number of moles, we can neglect the further dilutions)

0.0005 moles of H2SO4 are present in unknown solution

Converting it into Molarity (ie number of moles in 1000 mL)

(0.0005/10) x 1000 = 0.005 M

The concentration of unknown sulfuric acid is 0.005 M