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Laboratory preparation of NH3 and CO2 gas

Laboratory preparation of Ammonia gas(NH3)


Principle:

In the laboratory, ammonia gas is prepared by heating the mixture of ammonium chloride and calcium hydroxide(slaked lime) in the ratio 2:1.

   2NH4Cl + Ca(OH)2 ----> Cacl2 + 2H2O + 2NH3(g)


Apparatus required:-

  1. Hard glass test tube

  2. Delivery tube

  3. Gas jar

  4. Bunsen Burner

  5. Stand

  6. Red litmus Paper

  7. Cork

  8. Lime tower


Chemicals required:-

  1. Ammonium Chloride [NH4Cl]

  2. Calcium Hydroxide [ca(OH)2]


Diagram for apparatus arrangement:-


Procedure:-

  1. Prepare a mixture of ammonium chloride and calcium hydroxide in the ratio 2:1.

  2. Keep the mixture in a hard glass test tube.

  3. Arrange the apparatus well and supply the heat using Bunsen Burner.

  4. After this, Ammonia gas is produced and collected in a gas jar by the downward displacement of air.


Precautions:-

  1. The apparatus should be made airtight.

  2. Ammonia gas is collected by downward displacement of air.

  3. The hard glass test tube should be slightly inclined.


Test of Ammonia gas:-

  1. Ammonia gas turns red litmus paper into blue because it is basic in nature.

  2. It forms a white fume of ammonium chloride (NH4Cl), when a glass rod dipped in conc. HCl is brought in contact with ammonia gas.

  3. It gives a strong pungent odour.


Laboratory preparation of Carbon dioxide gas (C02)


Principle:-

In the laboratory, Carbon dioxide gas is prepared by the reaction of dilute hydrochloric acid and calcium carbonate (limestone or marble).

CaCO3 + 2HCl ----> CaCl2 + H2O + CO2 (g)


Apparatus required :-

  1. Woulfe’s bottle,

  2. Gas jar

  3. Delivery tube

  4. Thistle funnel

  5. Match box

  6. Corks


Chemicals required:-

  1. dilute hydrochloric acid [HCl]  and 

  2. calcium carbonate (limestone or marble) [CaCO3]


Diagram for apparatus arrangement:-

Procedure:-

  1. Arrange the apparatus as shown and place some pieces of marble in Woulfe’s bottle.

  2. Pour some dil. Hydrochloric acid through the thistle funnel until it covers the lower end of the thistle funnel and the marble pieces.

  3. They react together and give off Carbon dioxide gas.

  4. This gas is passed through the delivery tube and collected in a gas jar by the upward displacement of air.


Precautions :-

  1. The apparatus should be made airtight.

  2. The lower end of thistle funnel should be dipped in solution.

  3. The lower end of the delivery tube should not touch the solution within the Woufle’s bottle.

  4. CO2 is collected in the gas jar by the upward displacement of air.


Test of CO2 gas:-

  1. If a burning match stick extinguishes when taken closer to the gas jar, it shows that the gas contained in the jar is Carbon dioxide.

  2. It turns moist blue litmus paper red, since it’s acidic in nature.

  3. When the gas formed i.e. CO2 is passed through lime water [Ca(OH)2], it turns milky white due to formation of insoluble calcium carbonate (CaCO3).

CO2 + Ca(OH)2 ----> CaCO3 + H2O

Also, when CO2 is passed through lime water for long, the milky colour disappears slowly due to formation of water soluble calcium bicarbonate [Ca(HCO3)2].

CaCO3 + H2O + CO2 ----> Ca(HCO3)2


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