Question

It takes 150mL of 5M sodium hydroxide to neutralize 250mL of sulfuric acid. What is the concentration of the sulfuric acid?

Answer 1

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

                                            = 5 M x (150/1000 ) L               Since 1L = 1000 mL

                                            = 0.75 mol

The reaction between NaOH & H₂SO₄ is given by

2NaOH + H₂SO₄ Na₂SO₄ + 2H₂O

According to the balanced equation ,

2 moles of NaOH reacts with 1 mole of H₂SO₄ for complete neutralization

0.75 moles of NaOH reacts with M mole of H₂SO₄ for complete neutralization

M = ( 0.75x1) / 2

   = 0.375 moles

So Molarity of f H₂SO₄ is , M = number of moles of f H₂SO₄ / volume of f H₂SO₄ in L

                                           = 0.375 mol / (250/1000) L

                                           = 1.5 M

Therefore the concentration of sulfuric acid is 1.5 M