Class 9 Separating the components of a mixture, How can we obtain different gases from air?

### Topics to be covered

=> Separating the components of a mixture
=> How can we obtain different gases from air?

### 𝐒𝐞𝐩𝐚𝐫𝐚𝐭𝐢𝐧𝐠 𝐭𝐡𝐞 𝐂𝐨𝐦𝐩𝐨𝐧𝐞𝐧𝐭𝐬 𝐨𝐟 𝐚 𝐌𝐢𝐱𝐭𝐮𝐫𝐞

color{green}("𝟏 𝐄𝐕𝐀𝐏𝐎𝐑𝐀𝐓𝐈𝐎𝐍:") Using evaporation method ,the volatile component (solvent) from its non-volatile solute by the method of evaporation.

color{red}("𝐎𝐁𝐒𝐄𝐑𝐕𝐀𝐓𝐈𝐎𝐍")

Due to evaporation method we can easily obtain the constituents of ink (mixture of dye and water).

color{green}("𝟐 𝐂𝐄𝐍𝐓𝐑𝐈𝐅𝐔𝐆𝐀𝐓𝐈𝐎𝐍 :") It is a method for the separation of suspended particles of a substance from a liquid in which the mixture is rotated at high speed in a centrifuge machine.

color{red}("𝐎𝐁𝐒𝐄𝐑𝐕𝐀𝐓𝐈𝐎𝐍")

The principle is that the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly. So the liquid being lighter will remain on the top and using this we can separate the cream from the milk.

color{red}("𝐀𝐩𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬")

color{green}(•) Used in diagnostic laboratories for blood and urine tests.

color{green}(•) Used in dairies and home to separate butter from cream.

color{green}(•) Used in washing machines to squeeze out water from wet clothes.

color{green}("𝟑 𝐒𝐄𝐏𝐀𝐑𝐀𝐓𝐈𝐎𝐍 𝐎𝐅 𝐓𝐖𝐎 𝐈𝐌𝐌𝐈𝐒𝐂𝐈𝐁𝐋𝐄 𝐋𝐈𝐐𝐔𝐈𝐃𝐒")

The principle is that immiscible liquids separate out in layers depending on their densities.

color{red}("𝐎𝐁𝐒𝐄𝐑𝐕𝐀𝐓𝐈𝐎𝐍")

Kerosene oil has lesser density as compared to that of water so it settles to the top of water and water can therefore be obtained first from the bottom by opening the stopcock of the funnel.

color{green}("𝟒 𝐒𝐔𝐁𝐋𝐈𝐌𝐀𝐓𝐈𝐎𝐍:") Mixtures that contain a sublimable volatile component can be separated from a non-sublimable impurity (salt in this case) using the sublimation process. Some examples of solids which sublime are ammonium chloride, camphor, naphthalene and anthracene.

color{green}("𝟓 𝐂𝐇𝐑𝐎𝐌𝐀𝐓𝐎𝐆𝐑𝐀𝐏𝐇𝐘:") Chromatography(Kroma in Greek means colour ) is the technique used for separation of those solutes that dissolve in the same solvent. This technique was first used for separation of colours, so this name was given.

color{red}("𝐎𝐁𝐒𝐄𝐑𝐕𝐀𝐓𝐈𝐎𝐍")
The ink that we use has water as the solvent and the dye is soluble in it. As the water rises on the filter paper it takes along with it the dye particles.
Usually, a dye is a mixture of two or more colours. The coloured component that is more soluble in water, rises faster and in this way the colours get separated.

color{red}("𝐀𝐩𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬 :")

Chromatography is used to separate

color{green}(•) colours in a dye

color{green}(•) pigments from natural colours

color{green}(•) drugs from blood

color{green}("𝟔 𝐒𝐄𝐏𝐀𝐑𝐀𝐓𝐈𝐎𝐍 𝐎𝐅 𝐌𝐈𝐗𝐓𝐔𝐑𝐄 𝐎𝐅 𝐓𝐖𝐎 𝐌𝐈𝐒𝐂𝐈𝐁𝐋𝐄 𝐋𝐈𝐐𝐔𝐈𝐃𝐒:")

Distillation is used for the separation of components of a mixture containing two miscible liquids that boil without decomposition and have sufficient difference in their boiling points.

color{green}("𝐅𝐑𝐀𝐂𝐓𝐈𝐎𝐍𝐀𝐋 𝐃𝐈𝐒𝐓𝐈𝐋𝐋𝐀𝐓𝐈𝐎𝐍")

Now for the separation of a mixture of two or more miscible liquids having the difference in boiling points less than 25 K, fractional distillation process is used, for example, for the separation of different gases from air, different factions from petroleum products etc. The apparatus is similar to that for simple distillation, except that a fractionating column is fitted in between the distillation flask and the condenser.

color{green}("𝟕 𝐂𝐑𝐘𝐒𝐓𝐀𝐋𝐋𝐈𝐒𝐀𝐓𝐈𝐎𝐍")

Crystallisation is a process that separates a pure solid in the form of its crystals from a solution.

Crystallisation technique is better than simple evaporation technique as –

color{green}(•) some solids decompose or some, like sugar, may get charred on heating to dryness.

color{green}(•) some impurities may remain dissolved in the solution even after filtration. On evaporation these contaminate the solid.

color{red}("𝐀𝐩𝐩𝐥𝐢𝐜𝐚𝐭𝐢𝐨𝐧𝐬")

color{green}(•) Purification of salt that we get from sea water.

color{green}(•) Separation of crystals of alum (phitkari) from impure samples.

In cities, drinking water is supplied from water works. A flow diagram of a typical water works is shown in Fig. 2.13.

### 𝐇𝐎𝐖 𝐂𝐀𝐍 𝐖𝐄 𝐎𝐁𝐓𝐀𝐈𝐍 𝐃𝐈𝐅𝐅𝐄𝐑𝐄𝐍𝐓 𝐆𝐀𝐒𝐄𝐒 𝐅𝐑𝐎𝐌 𝐀𝐈𝐑 ?

Air is a homogeneous mixture and can be separated into its components by fractional distillation.

color{green}(•) Liquid air can be obtained by increasing the pressure and decreasing temperature.

color{green}(•) This liquid air is then allowed to warm-up slowly in a fractional distillation column, where gases get separated at different heights depending upon their boiling points.