Question

An organic compound is subjected to chlorination to get compound A using 5.0 g of chlorine. When 0.5 g of compound A is reacted with AgNO$_3$ [Carius Method], the percentage of chlorine in compound A is _________ when it forms 0.3849 g of AgCl. (Round off to the Nearest Integer)
(Atomic masses of Ag and Cl are 107.87 and 35.5 respectively)

Hint:

In the Carius method, always calculate the mass of the halogen using: \[ \text{Mass of halogen} = \text{Mass of AgX} \times \frac{\text{Atomic mass of X}}{\text{Molar mass of AgX}} \] Ignore any extra data unless explicitly required.

Answer 1

Correct Answer: 19

The estimation of chlorine is carried out using the Carius method, in which chlorine present in the organic compound is converted completely into silver chloride (AgCl).
Step 1: Calculate the mass of chlorine from AgCl Molar mass of AgCl: \[ M_{\text{AgCl}} = 107.87 + 35.5 = 143.37\ \text{g mol}^{-1} \] Fraction of chlorine in AgCl: \[ \frac{35.5}{143.37} \] Given mass of AgCl formed: \[ = 0.3849\ \text{g} \] Mass of chlorine in the sample: \[ = 0.3849 \times \frac{35.5}{143.37} \approx 0.0952\ \text{g} \] Step 2: Calculate percentage of chlorine in compound A Mass of compound A taken: \[ = 0.5\ \text{g} \] \[ %\ \text{Cl} = \frac{0.0952}{0.5} \times 100 = 19.04% \] Step 3: Round off \[ \boxed{19} \]