Question

In the estimation of sulphur by Carius method, \(0.468 \mathrm{~g}\) of an organic sulphur compound afforded \(0.668 \mathrm{~g}\) of barium sulphate. Find out the percentage of sulphur in the given compound.

Short answer

The percentage of sulphur in the compound is approximately 19.61%.

Step-by-step solution

Calculate the Moles of Barium Sulphate Formed

To find the moles of \( \text{BaSO}_4 \), we use its molar mass. The molar mass of \( \text{BaSO}_4 \) is approximately \( 233 \, \text{g/mol} \). Calculate the moles using: \[ \text{Moles of } \text{BaSO}_4 = \frac{0.668 \, \text{g}}{233 \, \text{g/mol}} \approx 0.002868 \text{ mol} \]

Calculate the Moles of Sulphur in Barium Sulphate

In one mole of \( \text{BaSO}_4 \), there is one mole of sulphur. Therefore, the moles of sulphur is equal to the moles of \( \text{BaSO}_4 \): \[ \text{Moles of Sulphur} = 0.002868 \text{ mol} \]

Calculate the Mass of Sulphur

The molar mass of sulphur is \( 32 \, \text{g/mol} \). Use this to find the mass of sulphur: \[ \text{Mass of Sulphur} = 0.002868 \text{ mol} \times 32 \, \text{g/mol} = 0.091776 \, \text{g} \]

Calculate the Percentage of Sulphur in the Compound

The percentage of sulphur is calculated by dividing the mass of sulphur by the total mass of the compound, then multiplying by 100. \[ \text{Percentage of Sulphur} = \left( \frac{0.091776 \, \text{g}}{0.468 \, \text{g}} \right) \times 100 \approx 19.61\% \]

Key concepts

Barium sulphate

Barium sulphate (BaSO₄) is a white crystalline solid frequently used in chemical analysis and various industrial applications. It is practically insoluble in water, making it very stable. This compound is often utilized in tests to determine the presence and quantity of sulphur in organic compounds. During the Carius method, an organic compound containing sulphur is heated with fuming nitric acid, leading to the formation of barium sulphate as a precipitate. The formation of this precipitate is crucial, as it directly correlates to the amount of sulphur present in the sample. This unique characteristic of BaSO₄ is leveraged for precise measurements of sulphur content. Its insolubility helps in easily handling and weighing the precipitate, ensuring accurate results in quantitative analysis.

Molar mass

Molar mass plays a crucial role in chemical calculations and is defined as the mass of one mole of a substance. It is expressed in grams per mole (g/mol). For compounds like barium sulphate, knowing the molar mass helps us convert between mass and moles—an essential step in quantitative analysis.

When calculating molar mass, we sum up the atomic masses of all atoms in a molecule. In the case of BaSO₄:

• Barium (Ba) has an atomic mass of approximately 137 g/mol.
• Sulphur (S) has an atomic mass of about 32 g/mol.
• Oxygen (O) has an atomic mass of roughly 16 g/mol, multiplied by four (for four oxygen atoms in sulphate).

Putting it all together, the molar mass of BaSO₄ comes out to approximately 233 g/mol. Calculating this accurately ensures the correct conversion of grams to moles during the analysis, which is vital for determining the sulfur content in the original compound.

Sulphur estimation

Sulphur estimation using the Carius method is a reliable and precise process for identifying sulphur content in an organic compound. This method involves converting all sulphur in the compound to barium sulphate, providing a quantitative measure of sulphur.

The procedure begins by the combustion of the compound in the presence of nitric acid and barium chloride, resulting in the formation of water-insoluble BaSO₄. The amount of barium sulphate formed gives a direct measure of the sulphur amount in the original compound.

In the outlined example, the mass of formed BaSO₄ is used to calculate the moles, which directly indicates the moles of sulphur due to the 1:1 stoichiometry in BaSO₄. This forms the basis for determining the percentage of sulphur in the organic sample, a necessary computation in fields such as environmental sciences and industrial chemistry.

Organic compound analysis

Organic compound analysis is a broad subject Critical in various scientific fields. It helps in determining the composition and structure of organic molecules. Utilizing specific qualitative and quantitative methods allows researchers to identify the elements and their proportions within a compound.

In the context of the Carius method, this analysis is specifically targeted at identifying and quantifying sulphur in organic materials. By converting the sulphur to barium sulphate, we obtain quantitative data about sulphur content. Researchers utilize this information for various applications, including but not limited to, formulating pharmaceuticals, environmental monitoring, and developing industrial chemicals. This method provides a clear path from raw sample analysis to accurate comprehensive data, making it an invaluable tool in scientific exploration.