In sulphur estimation, 0.471 g of an organic compound gave 1.4439… — Solution | JEE Chemistry

NVAEasyJEE 2023Quantitative Analysis (C, H, N…)

In sulphur estimation, $0.471 \, \text{g}$ of an organic compound gave $1.4439 \, \text{g}$ of barium sulphate. The percentage of sulphur in the compound is _____ (Nearest Integer).

Given: Atomic masses: Ba = $137$ , S = $32$ , O = $16$ .

Answer

Correct answer:42

Step-by-step solution

Standard Method

Given: Mass of organic compound = $0.471 \, \text{g}$ , mass of BaSO $_4$ formed = $1.4439 \, \text{g}$ .

Find: Percentage of sulphur in the compound.

First, calculate the molar mass of barium sulphate:

M(\text{BaSO}_4) = 137 + 32 + 64 = 233 \, \text{g/mol}

The mass of sulphur present in BaSO $_4$ is:

\text{Mass of S} = \frac{32}{233} \times \text{mass of BaSO}_4

Substituting the given mass:

\text{Mass of S} = \frac{32}{233} \times 1.4439 = 0.1984 \, \text{g}

Now calculate the percentage of sulphur in the compound:

\%\,\text{S} = \frac{\text{Mass of S}}{\text{Mass of compound}} \times 100 = \frac{0.1984}{0.471} \times 100 = 42.10\%

Therefore, the percentage of sulphur in the compound is $42\%$ , so the nearest integer answer is $42$ .

Common mistakes

Using the full molar mass of BaSO $_4$ incorrectly. The sulphur mass must be found using the fraction $\frac{32}{233}$ , not by taking the entire $1.4439 \, \text{g}$ as sulphur. Always use the stoichiometric mass ratio.
Calculating the percentage with the wrong denominator. The percentage of sulphur must be computed using the mass of the original organic compound, $0.471 \, \text{g}$ , not the mass of BaSO $_4$ . Use $\frac{\text{mass of S}}{\text{mass of compound}} \times 100$ .

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Answer

Step-by-step solution

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