Question

0.4 gm organic compound is subjected to estimation of sulphur by Carius method. In the process \(0.6\) gm of \(BaSO_4\) was formed. Find \% of sulphur (nearest integer).

• A. 18
• B. 21
• C. 24
• D. 27

Answer 1

The Correct Option is B

Concept:
In the Carius method, sulphur present in an organic compound is oxidised to sulphate and finally precipitated as \(BaSO_4\). The amount of sulphur in the compound is calculated using stoichiometric relation between \(BaSO_4\) and sulphur. Molar mass of \(BaSO_4 = 233\,g\,mol^{-1}\). Step 1: Calculate moles of \(BaSO_4\) formed. \[ \text{Moles of } BaSO_4 = \frac{0.6}{233} \] Each mole of \(BaSO_4\) contains one mole of sulphur. \[ n_S = \frac{0.6}{233} \] Step 2: Calculate mass of sulphur present. Atomic mass of sulphur \(= 32\). \[ W_S = \frac{0.6}{233}\times 32 \] \[ W_S = \frac{0.6 \times 32}{233} \] Step 3: Calculate percentage of sulphur. \[ \%S = \frac{\text{Mass of S}}{\text{Mass of compound}}\times 100 \] \[ \%S = \frac{\left(\frac{0.6\times32}{233}\right)}{0.4}\times100 \] \[ \%S = 20.6 \approx 21 \] \[ \boxed{21\%} \]