Question

1. Determine the concentration of H₂SO₄ when 10 mL of the surround water was collected near the C & H Sugar Company. Your sample was titrated with 5 ml of 0.5 Molar NaOH solution to neutral the pH. Determine the concentration of H₂SO₄ in your water sample.

Answer 1

Step-1

The titration of H₂SO₄ by NaOH takes place as,

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

At the equivalence point, the hydronium (H⁺) ion of strong acid is completely neutralized by equal number of moles of hydroxyl (OH^-) ion of NaOH to form water, and the pH of this solution is 7 i.e. neutral pH. Thus, at equivalence point,

                                  Moles of H⁺ = Moles of OH^-  

Again, H₂SO₄ dissociates to give 2 moles of H⁺, so,

                              2 x Moles of H₂SO₄ = Moles of NaOH

Also, number of moles = Molarity x Volume of solution

Thus, we can write for the above neutralization reaction as,

                          2 x Molarity of H₂SO₄ x Volume of H₂SO₄ = Molarity of NaOH x Volume of NaOH

Step-2

We have, molarity of NaOH = 0.5 M

                volume of H₂SO₄ = 10 mL

                volume of NaOH = 5 mL

Now, rearranging the above relation and substituting the known values,

                          

Therefore, the concentration of H₂SO₄ is 0.125 M.