Q.Give a brief description of the principles of the following techniques taking an example in each case:

'Chromatography' comes from Greek 'chroma' (colour) + 'graphein' (to write), because the technique was first developed to separate coloured substances.

Chromatography is a widely used technique for separating, purifying, and identifying the components of a mixture, based on differences in how strongly they interact with a stationary phase versus a mobile phase. The name reflects its historical origin: the Russian botanist Mikhail Tsvet used the technique in the early 1900s to separate coloured plant pigments (like chlorophylls and xanthophylls) as distinct coloured …

Sublimation is both the phenomenon of solid-to-vapour transition (without a liquid stage) and the purification technique that exploits it.

Certain solids, such as camphor, naphthalene, anthracene, benzoic acid, and iodine, possess a significant vapour pressure even in the solid state and convert directly to vapour on heating, bypassing the liquid state entirely; on cooling, the vapour re-solidifies directly (sublimes back). This property is used as a purification technique called sublimation: a mixture containing a sublimable solid and non-sublimab …

A mixture of ethyl alcohol and methyl alcohol is separated by fractional distillation.

Ethanol (b.p. ≈ 78 C) and methanol (b.p. ≈ 65 C) are completely miscible liquids whose boiling points differ by only about 13 C. Two miscible liquids with boiling points fairly close together are separated using a fractionating column, which provides repeated vaporisatio …

Sublimation is the standard method used to separate naphthalene from benzoic acid.

Naphthalene is a volatile solid that sublimes readily on gentle heating (passing directly from solid to vapour without melting), while benzoic acid does not sublime under the same mild conditions. Heating the mixture causes naphthalene vapours to rise and be collected/condensed separately (e.g. on a cold surface), leaving the …

The statement is True: chromatography separates the components of a mixture based on their differing rates of movement between a stationary and a mobile phase.

Chromatography is a widely used separation and purification technique in which a mixture, dissolved in a suitable solvent (mobile phase), is passed over a stationary phase (such as paper, silica, or alumina). Different components of the mixture move at different rat …

The method is called sublimation, used to separate a sublimable (volatile) solid from a non-volatile solid.

Some solids (e.g. camphor, naphthalene, iodine, ammonium chloride) pass directly from the solid state to the vapour state on heating, without passing through the liquid state — this property is called sublimation.

To separate a mixture of a volatile (sublimable) solid and a non-volatile solid: the mixture is heated gently in a china dish covered with an inverted funnel (its stem plugged with cotton wool). The volatile solid sublimes and its vapours rise, striking the cooler surface of the funnel/watch glass, where they condense back into solid form (deposit as crystals). The non-volatile solid is left behind in the dis …

Paper chromatography works on the principle of partition — components distribute differently between the stationary phase (water in the paper) and the mobile phase (solvent).

In paper chromatography, a strip of filter paper acts as the stationary phase (its cellulose fibres hold a thin film of water), while a suitable solvent acts as the mobile phase, moving up (or along) the paper by capillary action.

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Paper chromatography is a partition technique: the paper's cellulose fibres absorb and hold water as the stationary phase, and components of a mixture distribute (partition) between this absorbed water and the flowing solvent, based on the printed choice of 'adsorption' or 'absorption', the correct answer is absorption.

Chromatography techniques are broadly of two kinds:

• Adsorption chromatography (e.g. column chromatography with alumina/silica, thin-layer chromatography): the stationary phase is a solid surface, and separation happens because different components are adsorbed onto that solid surface with different strengths.
• Partition chromatography (e.g. paper chromatography): the stationary phase is a liquid (here, water) held by absorption within the pores/fibres of an inert support (the paper). Components separate because they distribute (partition) differently between this stationary liquid and the mobile solvent that flows over the paper by capillary action. …

Sublimation is the direct solid-to-vapour phase change (and its reverse, vapour-to-solid) without an intermediate liquid stage; it is also used as an organic-chemistry purification technique.

Most solids melt into a liquid before they can vaporise. However, certain substances (such as camphor, naphthalene, ammonium chloride, and iodine) possess a vapour pressure high enough that, on heating, they pass directly into the vapour phase without forming a liquid in between. This process is called sublimation. In organic chemistry it is exploited as a purificat …

Distillation purifies a liquid by heating it to vaporise the liquid component and then condensing the vapours, separating it from non-volatile or higher-boiling impurities.

Distillation is one of the standard purification techniques taught for organic compounds. The impure liquid is heated in a distillation flask; the more volatile component vaporises first, travels through a condenser where it is cooled and converted back into a liquid, and is collected separately as the distillate. Non-volatile impurit …