Purification and Characteristics of Organic Compounds MCQs for NEET — Chemistry Questions with Answers

The yellow color observed during the detection of phosphorus in an organic compound is due to the formation of ammonium phosphomolybdate, which has the chemical formula \((NH_4)_3PO_4 \cdot 12MoO_3\). This compound is a characteristic yellow precipitate that confirms the presence of phosphorus.

$ MW = { 108 \times 0.306 \over 0.216 } - 107 = 46 $

To find the molecular weight of the acid, we use the mass of the silver salt and the mass of silver obtained upon ignition. The tribasic acid forms a silver salt with 3 Ag atoms. The formula weight of silver (Ag) is 108 g/mol. The mass of silver in the salt is 0.648 g, which corresponds to 3 moles of Ag (since it's a tribasic salt). Therefore, the equivalent weight of the acid can be calculated as follows: \((1.026 / 0.648) imes 108 / 3 = 192\). Thus, the molecular weight of the acid is 192 g/mol.

Chromatography is a versatile technique used for the separation and purification of various substances. It can be used to purify solids, liquids, and gases. This is because chromatography relies on the differential partitioning between the mobile and stationary phases, making it effective for a wide range of substances.

Beilstein’s test is used for the detection of halogens in an organic compound. In this test, a copper wire is heated in a flame until it stops producing a green flame. Then the wire is dipped into the organic compound and reheated in the flame. If a green flame reappears, it indicates the presence of halogen in the compound.

To separate a solution of benzene and chloroform, distillation is the most appropriate method. Benzene and chloroform have different boiling points (benzene boils at 80.1°C, while chloroform boils at 61.2°C). Distillation allows them to be separated based on these differences in boiling points.

Fractional Crystallisation is the method used to separate a mixture of KCl and $KClO_3$. This technique is based on the different solubilities of KCl and $KClO_3$ in water. By carefully controlling the temperature, one can selectively crystallise one component from the mixture, leaving the other in solution.

Middleton’s test is used to detect Sulfur (S). This test involves converting sulfur compounds into sulfur dioxide ($SO_2$) and then using barium chloride to detect the presence of sulfur dioxide by forming a white precipitate of barium sulfate.