TO PREPARE AMMONIA GAS IN LABORATORY AND TO STUDY ITS PROPERTIES

APPARATUS REQUIRED:

i) Round bottom flask

ii) Gas Jar

iii) Test tube stand

iv) Tripod stand

v) Delivery tube

vi) Cork

vii) Test tube

viii) Wire gauge.

CHEMICALS REQUIRED:

i)Ammonium chloride (NH₄Cl)

ii) Calcium hydroxide or slaked lime Ca(OH)₂

iii) Conc. HCl

iv) CuSO₄  solution

v) FeCl₃ solution

vi) FeSO₄  solution

vii) Mercurous nitrate solution

viii) Phenolphthalein solution

THEORY:

Ammonia gas is prepared in laboratory by heating the mixture of ammonium chloride (NH₄Cl) and calcium hydroxide Cu(OH)₂  in the ratio 1:2 by weight as:

triangle

2NH₄ Cl+ Cu(OH)₂ —————–> CuCl₂ + 2NH₃ ↑ + 2H₂O

Ionic reaction

NH₄⁺ (aq) + OH^–(aq) ————>NH₃ ↑ + H₂O

The gas formed is collected underwater as it is in the  gas jar by downward displacement of air, as the gas is lighter than air.

The gas cannot be collected underwater as it is highly soluble in water. If dry ammonia gas (NH₃) is to be prepared than ammonia gas should be dried by passing through lime towers but anhydrous CuCl₂ as well as Conc. H₂SO₄ cannot be used as a drying agent, it is because they react with ammonia.

NH3+ Conc. H₂SO₄  ——————> (NH4)₂SO₄

Anhydrous CaCl₂ + NH₃ ————->  CaCl₂. 8NH₃

[octa anime calcium chloride]

PROCEDURE:

The mixture of ammonium chloride (NH₄Cl) and calcium hydroxide Ca(OH)₂ in the ratio 1:3 by weight in the form of paste was taken in a round bottom flask. Then the flask was fitted with a delivery tube and set in a slight slanting position supported by a stand with clamp as shown in figure. The whole mixture was then heated, ammonia (NH₃) gas produced was passed through the delivery tube and finally collected in the gas jar by downward displacement of air. Thus, collected NH₃ gas was used to study its properties.

OBSERVATION TABLE:

S.N.	Experiment	Observation	Inference
1.	Color of the was noted.	No color was observed.	Ammonia gas is colorless.
2.	Odor of gas was tested.	Ringent smell was noted.	The Ammonia gas is pungent in smell.
3.	Moist red and blue litmus paper were introduced to the gas.	Red litmus paper, turnedto blue but most bluewas observed to notchange in color.	Ammonia gas is basic in nature.
4.	Burning match stickwas introduced to the gas.	The match was extinguished and gas was observed to not burn.	Ammonia gas is neither combustible nor a supporter of burning.
5.	A gas jar filled with NH3 gas was inverted over water and was shaken up and down.	Water level was observed rising inside the gas jar.	Ammonia gas is highly soluble in water.
6.	NH3 gas was passed in a test tube containing CuSO4 solution for a short time.	Bluish white ppt was obtained.	Cupric hydroxide Cu(OH)2 is formed.
7.	Few drops of conc. HCl was taken in a test tube and NH3 gas was passed into it.	Dense white fumes were observed.	Ammonium chloride is formed.
8.	The NH3 gas was passed in a test to be containing CuSO4 solution for long time.	Brown ppt. was observed.	Ferric hydroxide Fe (OH)3 is formed.
9.	Ammonia gas was passed through the FeSO solution.	Dirty green ppt.was obtained.	Ferrous hydroxide Fe (OH)2 is formed.
10.	Ammonia gas was passed over wet-filter paper with mercuric nitrate solution.	The wet filter paper was observed turning into black.	Monobasic ammonium mercuric nitrate and finely divided mercury is formed.
11.	Ammonia gas was passed into Nessler’s reagent test tube.	Reddish brown ppt was observed.	Millon’s base is formed.
12.	The gas was passed into a few drops of phenolphthalein solution in a test tube.	Colorless phenolphthalein was turned into pink.	Ammonia gas is basic in nature.
13.

REACTION INVOLVED:

NH₃ + H₂O ————> NH₄OH —right left harpoons—— NH₄⁺ + OH^–

Ammonium hydroxide

NH₃ + Conc. HCL —————-> NH₄Cl

Ammonium chloride

(dense with fumes)

                                 For short time 

CuSO₄ + 2NH₄OH ———————–> Cu (OH)₂ ↓+ (NH₄)2SO₄

Cupric hydroxide

(Bluish white ppt)

    long time

Cu(OH)₂ + (NH₄)2SO₄ + NH₄OH ——————> [Cu(NH₃)₄] SO₄ +H₂O

[Tetraamine copper (11) sulpbate ]

(Deep blue colour)

FeCl₃ + 3NH₄OH —————–> Fe (OH)₃ ↓ + (NH₄)₂ SO₄

Ferrous hydroxide

(Dirty green ppt)

Hg₂(NO₃)₂ +2NH₃ ————–> [Hg + Hg (NH₂) NO₃ ] + NH₄ NO₃

  [ Mercuric Amino Nitrate ]

(Black ppt)

NH₃ + 2KHgI₄ + 3KOH ———–> NH₂Hg OHgI + 7KI+2H₂O

     [Millon’s base]

     (brown ppt)

RESULT:

Hence, Ammonia gas was prepared in the laboratory and it’s properties were studied..

CONCLUSION:

In this way, Ammonia gas can be prepared in the laboratory by heating the mixture of NH₄CL and Ca(OH)₂ and its properties can be studied.

PRECAUTIONS:

1) The apparatus should be neat and clean.

2) Apparatus must be handled carefully.

3) The apparatus should be airlight.

4) Heat should be given gently.

5) R.B Flask should be clamped at an incline