Chemistry [2 Mark Question Answer]

(i) Ammonia burns with a yellowish flame. It produces water vapour and nitrogen.
(ii) When ammonium hydroxide is brought near the mouth of concentrated hydrochloric acid, it produces dense white fumes of ammonium chloride.

The gases which leave the catalyst chamber contain ammonia and unreacted nitrogen and hydrogen gas. The gases leaving the catalyst chamber are cooled by passing through condensing pipes where ammonia gets liquefied and is collected in receiver.

(a) Aqueous solution of ammonia turns red li tmus blue stating that it is having basicions.
(b) It precipitates hydroxides of metals.

Aqueous solution is acidic in nature due to presence of hydrogen ion.
Aqueous solution of ammonia is weakly basic in nature due to presence of hydroxylion.

During laboratory preparation of ammonia, it is passed through a drying tower containing quicklime (calcium oxide).
Ammonia is collected in an inverted dry gas jar by the downward displacement of air.

(i) Ammonia is used in the manufacture of fertilisers such as ammonium sulphate ammonium nitrate, etc.
(ii) It is used in the industrial preparation of nitric acid by Ostwalds process.

Ammonia is the odd one out.
Ammonia forms weakly basic solution when dissolved in water.
The others give acidic solution when dissolved in water.

Test of ammonia and ammoniumions:
(i) Ammonia gas has a characteristic pungent smell
(ii) A glass rod dipped in concentrated hydrochloric acid and is introduced into the gas produces thick white fumes of ammonium chloride.

 

Dry ammonia	Aqueous ammonia
Dry ammonia is neutral to indicators.	Aqueous ammonia shows alkaline or basic behaviour with indicators. It turns red li tmus blue.

The gases leaving the catalyst chamber are cooled by passing through
condensing pipes where ammonia gets liquefied and is collected in
receiver.
Key: Habers Process

(i) Finely divided iron acts as catalyst which alters the rate of reaction,
but itself does not undergo any chemical change.
(ii ) Molybdenum acts as promoter which increase the efficiency of
the catalyst.

Source of hydrogen : Hydrogen is generally obtained from water gas by
Bosch process.
Source of nitrogen : Nitrogen is obtained from air by its liquefaction and
fractional distillation .

Ammonium hydroxide precipitates hydroxides of metals, which differ in
colour and solubility in excess of ammonium hydroxide. Thus it is used
inidenti fication of metalions.

A promoter is a substance that is added to increase the efficiency of a
catalyst.

Liquid ammonia is a polar covalent compound and neutral to li tmus.
Liquor ammonia is solution of ammonia in water, which is weakly basic
in nature. It turns red litmus blue.

Calcium hydroxide is preferred as it is cheap and not deliquescent like
NaOH or KOH.

Ammonium nitrate is explosive in nature and it decomposes to give
nitrous oxide and water. Thus, it is not used in the laboratory
preparation of ammonia.

Once the reaction starts, further heating is not required because the
reaction is exothermic. The heat evolved is sufficient to maintain the
optimum temperature.

Ammonia is found both in free state and in combined state. In free state, it is formed in traces amount by decaying urine and other organic matter.
In combined state, ammonia is found as ammonium salts mainly as ammonium chloride and ammonium sulphate.