What is the Molarity?

Question

In a titration, a sample of H₂SO₄ solution having a volume of 20.48 mL required 36.26 mL of 0.169 M NaOH solution for complete neutralization.

What is the molarity of the H₂SO₄ solution?

Answer 1

Write the correctly balanced equation for the reaction taking place:

H2SO4 + 2NaOH ==> Na2SO4 + 2H2O

We are asked to find the molarity of H2SO4, and molarity means moles H2SO4/liter of solution. We already know the liters of solution which is 20.48 mls H2SO4 x 1 L/1000 ml = 0.02048 liters of solution. So, we must find moles of H2SO4.

We can find moles of H2SO4 by first finding moles of NaOH used and from the balanced equation we see that 2 moles NaOH reacts with 1 mole H2SO4

Moles NaOH = 0.03626 L x 0.169 mol/L = 0.006128 moles NaOH

Moles H2SO4 present = 0.006128 mol NaOH x 1 mol H2SO4/2 mol NaOH = 0.003064 mol H2SO4

Molarity of H2SO4 solution = 0.003064 mole/0.02048 L = 0.1496 M = 0.150 M (to 3 significant figures)