Question

A 25.00 mL sample of an H2SO4 solution of unknown concentration is titrated with a 0.1322 M KOH solution. A volume of 41.22 mL of KOH is required to reach the equivalence point. What is the concentration of the unknown H2SO4 solution? Express your answer in molarity to four significant figures.

Answer 1

Number of moles of KOH , n = Molarity x volume in L

                                          = 0.1322 M x (41.22/1000) L

                                         = 5.45x10^-3 mol

The reaction between KOH & H₂SO₄ is : 2KOH + H₂SO₄ K₂SO₄ + 2H₂O

According to the balanced equation ,

2 moles of KOH reacts with 1 mole of H₂SO₄

5.45x10^-3 mol of KOH reacts with M mole of H₂SO₄

M = ( 1x= 5.45x10^-3 ) / 2

    = 2.72x10^-3 mol

So the number of moles of H₂SO₄ reacted with KOH is 2.72x10^-3 mol

Given volume of H₂SO₄ sample is 25.00 mL = 25.00/1000 = 0.025 L

So concentration of H₂SO₄ , M = number of moles / volume of H₂SO₄ in L

                                              = ( 2.72x10^-3 mol) / 0.025 L

                                              = 0.1089 M

Therefore the molarity of unknown solution is 0.1089 M