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

In an organic compound, phosphorus is often estimated as magnesium pyrophosphate ( ext{Mg}_2 ext{P}_2 ext{O}_7). This compound is formed during the process of phosphorus analysis, where the organic sample is typically combusted, and the phosphorus is precipitated and weighed as magnesium pyrophosphate.

Distillation is a technique of purification of organic compounds. It involves heating a liquid to create vapor and then condensing the vapor back into a liquid. This method is commonly used to separate mixtures based on differences in their boiling points.

Both chromatography and spectroscopy are methods used to check the purity of organic compounds. Chromatography separates components of a mixture based on their movement through a stationary phase, while spectroscopy analyzes the interaction of light with the sample to identify and quantify the compounds present.

Crystallization is a purification technique based on the difference in the solubilities of the compound and the impurities in a given solvent. During crystallization, the desired compound forms solid crystals from a solution, leaving impurities in the solution.

For effective crystallization, the solvent should exhibit two main properties: the impure compound should be sparingly soluble in it at room temperature and appreciably soluble at higher temperatures. This ensures that upon cooling, the pure compound crystallizes out, leaving impurities in the solution.

Distillation is useful for separating liquids with a significant difference in their boiling points. This method relies on heating the mixture to vaporize the more volatile component, which is then condensed back into a liquid in a separate container.

To separate a mixture of chloroform (b.p 334K) and aniline (b.p 457K), distillation can be used. The substantial difference in boiling points allows for effective separation by selectively boiling and condensing each component.

To find the minimum molecular weight of insulin, we use the percentage of sulfur present. Given that insulin contains 3.4% sulfur, we assume the presence of one sulfur atom in the smallest unit of insulin. The atomic weight of sulfur is approximately 32 g/mol. Let's denote the minimum molecular weight of insulin as M. The percentage of sulfur can be expressed as (32/M) * 100% = 3.4%. Solving for M, we have M = (32 * 100) / 3.4 = 941.18. Since 941.18 is closest to option 940, the minimum molecular weight of insulin is approximately 940.

The Carius method is used for the quantitative determination of halogens (chlorine, bromine, and iodine), sulfur, and phosphorus in organic compounds. The organic compound is heated with fuming nitric acid in a sealed tube, resulting in the formation of silver halide (if halogens are present) which can be weighted. Therefore, the element estimated by the Carius method is Halogen.

Distillation under reduced pressure is used when a liquid has a very high boiling point and decomposes at or below its boiling point. The reduced pressure lowers the boiling point of the liquid, allowing it to be distilled without decomposition.