Test: Purification of Organic Compounds - NEET MCQ

A fractionating column is a crucial component in the process of fractional distillation. Here's how it works:

• Heat Exchange: The column is packed with materials like glass beads or plates that create a large surface area. As the liquid mixture is heated, vapors ascend through the column.

• Condensation and Revaporization: As these vapors rise, they cool down slightly as they come into contact with the surfaces within the column. This causes some of the vapors to condense back into liquid form. The heat from the rising vapors can then cause these condensed liquids to re-evaporate.

• Repeated Cycles: This process of condensation and evaporation repeats many times as the vapors move up the column. Each cycle results in the separation of components based on their boiling points, with the more volatile components rising higher in the column.

• Separation Efficiency: The fractionating column increases the efficiency of separating the components by providing multiple stages of condensation and vaporization. The more volatile components end up at the top of the column, while the less volatile components stay near the bottom.

In summary, the fractionating column's design allows for efficient separation of components in a mixture by providing numerous surfaces for heat exchange between the ascending vapors and descending condensed liquids. This is why it's the correct apparatus for this function.

In partition chromatography, the stationary phase is thin film of liquid adsorbed on an essentially inert support. Mobile phase may be a liquid or a gas.
Paper chromatography is an example of partition chromatography in which liquid present in the pores of paper is stationary phase and some other liquid is movable phase. Separation depends upon partition of substance between two phases and the adsorption effects of inert support on compounds undergoing chromatographic separation.

The correct answer is Option A.
 
Steam distillation is used to separate organic compounds that tend to decompose at high temperature. Essential oils can be purified by steam distillation.

The process by which an impure compound is converted into its crystals is known as crystallisation. It is based on the difference in the solubilities of the compound and the impurities in a suitable solvent.

All other are sublimatory substances. 

The Rf value is defined as the ratio of the distance moved by the solute and the distance moved by the the solvent along the paper, where both distances are measured from the common Origin or Application Baseline, that is the point where the sample is initially spotted on the paper.

Sublimation is a process of changing solid to gas and vice-versa. And when naphthalene changes into gas then impure substance would be left.

The correct answer is Option D.
Chromatography is an important separation technique used to separate constituent particles of a mixture of substances, to purify the compounds and check the purity of organic compounds. In this technique on a stationary phase (solid or a liquid) a mixture of substances is applied. The mixture of gas or the pure solvent is allowed to move slowly on the stationary phase. Due to which the components of the mixture start separating from one another.