Question

Write the names of the following compounds and deduce their molecular masses. 

(i) Na₂ SO₄ ,(ii) K₂ CO₃ ,(iii) CO₂ ,(iv) MgCl₂ ,(v) NaOH, (vi) AlPO₄ ,(vii) NaHCO₃

 

Answer 1

(i) Na₂SO₄ - Sodium sulphate.

Molecular mass= sum of masses of individual components

Atomic mass of, Na = 23u, S=32u, O=16u

∴ Molecular mass of Na₂SO₄ = 2x(23) + 32 + 4x(16)= 142u

(ii) K₂CO₃ - Potassium carbonate.

Atomic mass of, K=39u, C=12u, O=16u

∴ Molecular mass of K₂CO₃ = 2x(39) + 12 + 3x(16) = 138u

(iii) CO₂ - Carbon dioxide.

Atomic mass of, C=12u, O=16u

∴ Molecular mass of CO₂ = 12 + 2x(16) = 44u

(iv) MgCl₂ - Magnesium chloride.

Atomic mass of, Mg=24u, Cl=35.5u

∴ Molecular mass of MgCl₂ = 24 + 2x(35.5) = 95u

(v) NaOH - Sodium hydroxide.

Atomic mass of, Na=23u, O=16u, H=1u

∴ Molecular mass of NaOH = 23 + 16 + 1 = 40u

(vi) AlPO₄ - Aluminium phosphate

Atomic mass of, Al= 27u, P=31u, O=16u

∴ Molecular mass of AlPO₄ = 27 + 31 + 4x(16) = 122u

(vii) NaHCO₃ - Sodium bicarbonate

Atomic mass of, Na=23u, H= 1u, C=12u, O=16u

∴ Molecular mass of NaHCO₃ = 23 + 1 + 12 + 3x(16) = 84u