Question

Calculate the number of moles in 29.4 g of Sulphuric acid (H₂SO₄).

Answer 1

• The gram molecular mass is defined as the molecular mass of a mole of a substance expressed in grams.
• The relation between gram molecular mass, number of moles, and Avogadro's number is

The molar mass of a substance = 1 mole of that substance = 6.022×10²³ molecules.

• Number of moles of substance (n) = $\frac{\mathrm{Given}\mathrm{weight}\mathrm{of}\mathrm{substance}}{\mathrm{Molecular}\mathrm{weight}}$

The molecular weight of Sulphuric acid (H₂SO₄) = Atomic weight of individual components of Sulphuric acid (H₂SO₄).

i.e., Atomic weight of Hydrogen(H) =1, since there are 2 hydrogen atoms, Atomic weight =2×1=2g

Atomic weight of Sulphur(S) = 32 g

Atomic weight of Oxygen (O) = 16, since there are 4 oxygen atoms, Atomic weight = 16 × 4= 64g

Therefore the relative molecular weight of Sulphuric acid (H₂SO₄) = 2 + 32 + 64 = 98g

Given weight of Sulphuric acid (H₂SO₄) =29.4g

Therefore Number of moles of Sulphuric acid (H₂SO₄) =$\frac{29.4}{98}$ =0.3 moles.