Question

0.1254g of an organic compound gave 0.1292g of barium sulphate in the estimation of sulphur by Carius method. Find out the percentage of sulphur in the given organic compound.
(Atomic mass Ba=137;S=32;O=16)

Answer 1

Hint: In the above question we need to find the quantity of sulphur. This is quantitative analysis of organic compounds. We can calculate the mass % of sulphur present in the organic compound by using the formula mentioned below:
Mass % of sulphur = $\text{32 x }{{\text{m}}_{1}}\text{ x }\dfrac{100}{233\text{ x m}}$
Where,
${{\text{m}}_{1}}$ is the mass of barium sulphate,
$\text{m}$ is the mass of organic compound containing sulphur

Complete answer:
Quantitative analysis is an analysis method that we can use to determine the quantity of the elements or molecules produced during the chemical reaction. Organic compounds consist mainly of carbon and hydrogen.
It also comprises elements like oxygen, nitrogen, phosphorus, sulphur and halogens like chlorine, bromine, fluorine, iodine.
Carius Method:
- Heat a known mass of the organic compound containing sulphur in carius tube.
-This tube has sodium peroxide or hot conc nitric acid.
-The Sulphur present in the organic compound is converted to sulphuric acid due to oxidation.
-Sulphur is then precipitated in the form of barium sulfate when barium chloride solution is added. We then weigh the barium sulfate formed and make a note of it.
It is given that the mass of organic compound ($\text{m}$) is 0.1254g, mass of barium sulfate (${{\text{m}}_{1}}$) is 0.1292g.
Substituting the values in the formula,
Mass % of sulphur = $\text{32 x 0}\text{.1292 x }\dfrac{100}{233\text{ x 0}\text{.1254}}$ = 14.15
The percentage of sulphur in the organic compound is 14.15.

Therefore, the correct answer is option (C).

Note:
Carius method is used for quantitative analysis of halogens. The procedure is as follows:
- Heat the organic compound containing halogen along with fuming nitric acid and silver nitrate solution in the carius tube.
- Carbon and hydrogen present are oxidized to carbon dioxide and water. The halogen present in the organic compound reacts with silver nitrate to form respective silver halides. We weigh the mass of silver halide formed and then perform the calculations as we did for the estimation of Sulphur in the organic compound.