Question

3.15.8 cm3 of H2SO4 completely neutralised 20 cm3 of NaOH. The NaOH was 1.5 mol/dm3.

Answer 1

Answer:

Molarity = 0.95 mol/dm³

Explanation:

Given data:

Volume of H₂SO₄ = 15.8 cm³

Volume of NaOH = 20 cm³

Concentration of NaOH = 1.5 mol/dm³

Concentration of H₂SO₄ = ?

Solution:

Chemical equation:

NaOH + H₂SO₄      →          Na₂SO₄ + H₂O

First of all we will calculate the number of moles of NaOH and for that we will convert the units first,

Volume = 20 cm³/1000 = 0.02 L

Concentration of NaOH = 1.5 mol/dm³

1 mol/dm³ = 1 mol/L

Concentration of NaOH = 1.5 mol/L

Number of moles of NaOH:

Molarity = number of moles / volume in L

1.5 M = number of moles / 0.02 L

Number of moles = 1.5 M ×0.02 L

Number of moles = 0.03 mol

Now we will compare the moles of NaOH and H₂SO₄

                     NaOH           :        H₂SO₄

                         2               :           1

                     0.03             :        1/2×0.03 = 0.015 mol

Concentration of H₂SO₄:

Volume of H₂SO₄:

15.8 cm³/1000 = 0.0158 L

Molarity = number of moles / volume in L

Molarity = 0.015 mol / 0.0158 L

Molarity = 0.95 mol/L

1 mol/L = 1 mol/dm³

Molarity = 0.95 mol/dm³