Calculate the solubility of Na₂CO₃ at 25°C, if 20.0cm³ of it’s saturated solution at that temperature gave 1.75g of the anhyrous salt. [C=12, O=16…

JAMB Chemistry 2024 234 views
Source: JAMB · 2024

Calculate the solubility of Na₂CO₃ at 25°C, if 20.0cm³ of it’s saturated solution at that temperature gave 1.75g of the anhyrous salt. [C=12, O=16, Na = 23]

  1. 0.825 ✓
  2. 0.625
  3. 0.525
  4. 0.425
Explanation

Solubility is shown here in mol/dm³, so convert the mass to moles per litre.

20.0 cm³ gave 1.75 g. So 1000 cm³ holds 1.75 × 1000 ÷ 20 = 87.5 g.

Molar mass of Na₂CO₃ = 2(23) + 12 + 3(16) = 106 g/mol.

Solubility = 87.5 ÷ 106 ≈ 0.825 mol/dm³.

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