SS2 Chemistry Lesson Note on Ammonia: Laboratory and Industrial Preparation

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COMPOUNDS OF NITROGEN-AMMONIA LABORATORY AND INDUSTRIAL PREPARATION

 OXIDES OF NITROGEN

The common oxides of nitrogen are:-Dinitrogen(i) oxide, N₂O- Nitrogen (ii) oxide, NO. Nitrogen (iv) oxide, NO₂, others are dinitrogen(iii) oxide, N₂O_3, a pale blue liquid at room temperature and dinitrogen(iv) oxide, N₂O₄, a yellow liquid below the room temperature and dinitrogen(v) oxide N₂O₅ that exists as an unusual white solid at room temperature.

 AMMONIA

 INDUSTRIAL PRODUCTION OF AMMONIA

 The Haber process: Ammonia is manufactured from its constituent elements by a process devised by a German chemist, Fritz Haber (1914). The raw materials used are: nitrogen (obtained from water gas or natural gas).A mixture of dried nitrogen and hydrogen in the ratio 1:3  by volume is subjected to a high pressure of 200 – 250 atmosphere, at about 450  and in the presence of finely divided iron as the catalyst; the reaction is exothermic and reversible

N_2(g) + 3H_2(g)     →   2NH_3(g)

Under these conditions, about 20% ammonia is produced.

Successive heating and cooling under pressure liquefy the ammonia gas produced and the uncombined nitrogen and hydrogen are recycled. The flow chart for the production of ammonia is shown

Mixture in a drier

Mixture over finely Divided catalyst + heat + pressure

Ammonia liquefied and removed

 

LABORATORY PREPARATION OF AMMONIA:

Ammonia is prepared in the laboratory by heating a mixture of ammonium salt and non-volatile base. Calcium hydroxide is preferred to sodium hydroxide because calcium hydroxide is cheap and non-deliquescent. Heating a mixture of ammonium chloride and calcium hydroxide produces ammonia gas. The drying agent for ammonia is calcium oxide (quick lime). Concentrated tetraoxosulphate (vi) acid and calcium chloride are not used to dry ammonia because they react with ammonia to form salts

NH₄Cl  +  Ca(OH)₂    → CaCl₂  +  H₂O  +  NH₃

 EVALUATION

1. State the type of chemical bond between nitrogen and hydrogen atoms in a molecule of ammonia.
2. In the industrial production of ammonia.
3. What name is given to the process?
4. State one source of each of the starting material.
5. What are the operating temperature and pressure?

PERIOD 4: PROPERTIES AND USES, TEST FOR AMMONIA, FOUNTAIN EXPERIMENT

PHYSICAL PROPERTIES OF AMMONIA:

1. It is a colourless gas with choking smell.
2. It is very soluble in water.
3. In large quantities, ammonia is poisonous.
4. It is 1.7 times less dense than air
5. It turns moist red litmus paper red.

CHEMICAL PROPERTIES OF AMMONIA

1. Ammonia burns in oxygen producing steam and nitrogen

4NH₃ + 3O₂ →  2N₂ + 6H₂O

Ammonia reacts with platinium- rhodium catalyst to form nitrogen (ii) oxide.

4NH₃ + 5O₂     →  4NO + 6H₂O

2. Ammonia reduces copper (ii) oxide

2NH₃ + 3CuO  →  3Cu + 3H₂O + N₂

3. Ammonium precipitates many metallic ions from solution as insoluble hydroxides.

FeSO_4(aq) + 2NH_3(aq) + 2H₂O_(l)   →   Fe(OH)_2(s) +   (NH₄)₂SO_4(aq)

                                                                                             ^{green  ppt}

USES OF AMMONIA

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