When 50cm³ of a saturated solution of sugar (molar mass 342.0g) at 40°C was evaporated to dryness, 34.2g of dry solid was obtained. The solubility of…

JAMB Chemistry 2024 141 views

When 50cm³ of a saturated solution of sugar (molar mass 342.0g) at 40°C was evaporated to dryness, 34.2g of dry solid was obtained. The solubility of sugar at 40°C is

  1. 10.0 moles dm⁻³
  2. 7.0 moles dm⁻³
  3. 3.5 moles dm⁻³
  4. 2.0 moles dm⁻³ ✓

Explanation

To find the solubility in moles per dm³, first calculate the number of moles of sugar dissolved. Moles = mass ÷ molar mass = 34.2g ÷ 342.0g/mol = 0.1 mol.

Next, convert the volume of the solution from cm³ to dm³. Since 1 dm³ = 1000 cm³, we have 50 cm³ = 50 ÷ 1000 = 0.05 dm³.

Finally, calculate the concentration (solubility) in moles per dm³: Concentration = moles ÷ volume = 0.1 mol ÷ 0.05 dm³ = 2.0 moles dm⁻³. This is the amount of sugar that dissolves in one dm³ of solution at 40°C.

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