Chemistry MCQs for NEET — Practice Questions with Answers

$ \% Cl = { 35.5 \over 143.5 } \times { 0.287 \over 0.099} \times 100 $

When an organic compound containing sulfur is reacted with concentrated nitric acid (HNO3) for the estimation of sulfur, the sulfur is converted into sulfuric acid (H2SO4). This is due to the strong oxidizing nature of concentrated nitric acid, which oxidizes sulfur to its highest oxidation state in sulfuric acid.

Glycerol can be separated from spent-lye in the soap industry using distillation under reduced pressure. This method is preferred because glycerol has a high boiling point, and reducing the pressure lowers the boiling point, allowing the separation to occur without decomposition.

Steam distillation is used to separate aniline from water. Aniline and water form a heterogeneous mixture that can be separated by steam distillation because aniline is steam volatile and immiscible with water.

Chromatography is a versatile technique used to separate mixtures, purify compounds, and test the purity of compounds. It involves the partitioning of components between a stationary phase and a mobile phase, allowing for effective separation and analysis.

In chromatography, the term $ R_f $ stands for 'Retardation factor'. It is the ratio of the distance traveled by the solute to the distance traveled by the solvent front. It helps in identifying compounds based on their movement on the stationary phase.

The correct option is TTFF. (1) is True because silica gel is commonly used as an adsorbent in Thin Layer Chromatography (TLC). (2) is True because $ R_f $ indeed stands for Retardation factor. (3) is False because the adsorbent is a stationary phase, not a mobile phase. (4) is False because a chromaplate (TLC plate) is indeed a part of TLC.

In chromatography, ninhydrin solution is used to detect amino acids. Ninhydrin reacts with amino acids to produce a colored product, often purple or blue, which helps in visualizing the presence of amino acids on the chromatogram.

In the method of detecting carbon and hydrogen in an organic compound, the compound is heated with CuO (copper(II) oxide). The carbon present in the compound is oxidized to CO2, and the hydrogen is oxidized to H2O.

In the detection of carbon and hydrogen, the water produced is tested by anhydrous $ CuSO_4 $ (copper(II) sulfate). Anhydrous $ CuSO_4 $ is white and turns blue in the presence of water, indicating the formation of water.