Ncert Exercises & Solutions

Given below are two statements:

Assertion (A):	Sulphur present in an organic compound can be estimated quantitatively by the Carius method.
Reason (R):	Sulphur is separated easily from other atoms in the molecule and gets precipitated as a light yellow solid.

1.	Both (A) and (R) are true and (R) is the correct explanation of (A).
2.	Both (A) and (R) are true but (R) is not the correct explanation of (A).
3.	(A) is true but (R) is false.
4.	(A) is false but (R) is true.

Hint: Sulphur present in an organic compound can be estimated quantitatively by the Carius method

Sulphur present in an organic compound can be estimated quantitatively by the Carius method. In this method, a known

weight of the organic compound is heated with fuming HNO₃, S present in it gets converted into H₂SO₄. On adding BaCl₂,

H₂SO₄ gets precipitated as BaSO₄ which may be of light yellow or white in colour.

If light yellow colour is obtained, it means some impurities are present. It is then filtered, washed, purified and then dried

and finally, pure BaSO₄ of the white colour is obtained.

Thus, both assertion and reason are true and the reason is the correct explanation of assertion.