Match List I with List II:

The correct matching is:

A-iii, B-iv, C-ii, D-i

The correct answer is option 4. A-iii, B-iv, C-ii, D-i.

Let us go through each method and its corresponding application in detail:

A. Estimation of carbon and hydrogen in organic compound - iii. Liebig's method:

Liebig's Method: This method involves the combustion of the organic compound to determine the amount of carbon and hydrogen present. It's a standard technique used for elemental analysis to estimate the percentage of carbon and hydrogen in organic compounds.

B. Estimation of nitrogen in aniline - iv. Kjeldahl's method:

Kjeldahl's Method: This method is specifically used to estimate the nitrogen content in organic compounds, such as aniline. It involves digestion of the compound with sulfuric acid, which converts nitrogen into ammonium sulfate that is subsequently quantified.

C. Estimation of chlorine in carbon tetrachloride - ii. Carius method:

Carius Method: This method is used for the estimation of halogens, particularly chlorine in this case. It involves heating the organic compound with fuming nitric acid and silver nitrate, forming silver halide precipitates that are weighed to determine the chlorine content.

D. Detection of nitrogen, sulphur and halogens - i. Lassaigne's test:

Lassaigne's Test: This is a qualitative test used to detect the presence of nitrogen, sulfur, and halogens (chlorine, bromine, iodine) in organic compounds. It involves fusing the compound with sodium metal and then extracting the resulting fused mass with water. The extract is then tested for the presence of these elements.

Based on the explanations above, the correct matching of List I with List II is: 4. A-iii, B-iv, C-ii, D-i

A. Estimation of carbon and hydrogen in organic compound - iii. Liebig's method

B. Estimation of nitrogen in aniline - iv. Kjeldahl's method

C. Estimation of chlorine in carbon tetrachloride - ii. Carius method

D. Detection of nitrogen, sulphur and halogens - i. Lassaigne's test

This match correctly identifies each method with its specific application in organic compound analysis, either for estimation of specific elements or detection of their presence. Each method plays a crucial role in analytical chemistry for determining the composition and elements present in organic substances.