A 312 mg sample of an organic compound having a molar mass of 156 g mol ⁻¹ is subjected to Carius estimation, yielding 1398 mg of barium sulphate precipitate. The number of sulphur atoms present in one molecule of the compound is _______. (Given molar mass in g mol ⁻¹ of Ba : 137, S : 32, O : 16 )

Step-by-step solution

Molar mass of BaSO ₄ = 137 + 32 + 4 16 = 233 g mol ⁻¹ Millimoles of the organic compound taken = 312 mg 156 g mol ⁻¹ = 2 mmol Millimoles of BaSO ₄ formed = 1398 mg 233 g mol ⁻¹ = 6 mmol Since each mole of BaSO ₄ contains one mole of sulphur atoms, the millimoles of sulphur atoms present in the sample = 6 mmol . The number of sulphur atoms per molecule of the organic compound is the ratio of moles of sulphur atoms to the moles of the compound. Number of S atoms = 6 mmol 2 mmol = 3 Answer: 3