Gases – Carbon dioxide (CO2) and Ammonia(NH3) Preparation, Uses and Chemical Composition

You might have heard of the death of people due to suffocation during the cleaning of the deep wells. Similarly, you might have felt breathlessness inside the caves. What might be the causes of breathlessness inside the well? Which gas is used in refrigerators? Why is this gas used there? What may be the answers to these questions, let’s think for some time! We will discuss the gases like carbon dioxide and ammonia relate to these questions in this article.

Gases Definition

Gases are one of the four fundamental states of matter. They do not have definite shapes, sizes, and volumes because of weak intermolecular forces of attraction between the particles.

Carbon Dioxide Gas (CO₂)

Carbon dioxide is produced when coal, wood, kerosene, fat, oil, wax, etc. burns and gets mixed in the air. This gas is also produced during the respiration process of plants and animals, volcanic eruptions, and the decaying process of organic matter. Atmospheric air contains about 0,03% carbon dioxide by volume. Deforestation and burning of fuel are the artificial sources of carbon dioxide in the atmosphere. VanHelmont discovered carbon dioxide in 1630 AD by burning wood. Similarly, in 1755 AD, Joseph Black prepared this gas by burning magnesium carbonate. Later Lavoisier proved that carbon dioxide gas is a compound of carbon and oxygen.

Fact about Carbon dioxide gas

Symbol	Molecular Weight
CO2	44

Laboratory Preparation of Carbon Dioxide Gas

In the laboratory, carbon dioxide gas is prepared by the chemical reaction of limestone (CaCO3) with dilute hydrochloric acid (dil. HCL).

Calcium Carbonate + dilute Hydrochloric acid —————————————-> Calcium Chloride +water +Carbon dioxide

CaCO3 (s) +2HCL (aq)—————————————————————> Cacl2(aq) + H2O (l) + CO2 (g)

Apparatus Required

Wolfe’s bottle, gas jar, thistle funnel, delivery tube, rubber cork, and some test tubes.

Chemicals Required

Limestone or marble pieces or calcium carbonate powder or egg shells, dilute hydrochloric acid, phenolpthalein, lime water, sodium hydroxide solution, and blue litmus paper.

Method/Procedure

1. Collect the apparatus and chemicals required for the preparation of gas.
2. Keep some pieces of limestone or marble pieces or calcium carbonate powder or egg shells in Woulfe’s bottle.
3. Arrange the delivery tubes in one of the openings of Woulfe’s bottle and the delivery tube in another and make them airtight using rubber corks. Fix the delivery tube and thistle funnel in the opening of Woulfe’s bottle making it airtight with the help of rubber cork as shown in the figure.
4. …..
5. Pour dilute hydrochloric acid into the Woulfe’s bottle through the thistle funnel till it covers limestone or marble pieces or calcium carbonate powder or egg shells and the opening of the thistle funnel should be inside the acid layer.
6. Allow the gas to pass through the delivery tube and collect in the gas jar kept straight upright.
7. Observe the reaction between calcium carbonate and acid.
8. Carbon dioxide is formed during the reaction and the gas passes from Woulfe’s bottle to the gas jar through the delivery tube. This gas being heavier than air, it is collected in the gas by the upward displacement.

Precaution

• The end of the delivery tube should not be dipped into the acid.
• The end of the thistle funnel should be dipped into the acid.

Test of gas

• For a test of carbon dioxide, when a burning matchstick is brought near the mouth of the gas jar containing carbon dioxide, it extinguishes because carbon dioxide is neither combustible nor the supporter of combustion.
• When a moist blue litmus is brought near the mouth of the gas jar containing carbon dioxide, it turns blue. Similarly, when a few drops of phenolpthalein is put inside the gas jar, it remains colorless or unchanged. This proves that the gas jar is carbon dioxide.
• A little lime water is taken in a test tube and carbon dioxide is passed through it for some time, it changes into milky white. It is because of the formation of the insoluble calcium carbonate as a result of the reaction of carbon dioxide and calcium hydroxide of the lime water. On passing carbon dioxide for a long time, the milky white color disappears due to the formation of soluble calcium bicarbonate.

Properties of carbon dioxide gas

Physical properties

• It is an acidic or non-metallic oxide that is colorless and odorless.
• This gas dissolves in water to form carbonic acid, so it is sour in taste.
• It is slightly soluble in water.
• It is 1.5 times heavier than air.
• It shows acidic properties and changes moist blue litmus paper into red.
• This gas is nontoxic, however, organisms die in the environment of carbon dioxide by suffocation due to lack of oxygen gas.
• It can be changed into a liquid at high pressure and low temperature.
• When carbon dioxide is cooled below -78 degrees Celsius, it changes to a solid form which is known as dry ice.
• This gas is neither combustible nor supports combustion.

Chemical Properties

Carbon dioxide is neither combustible nor a supporter of combustion. It helps to extinguish the fire. But when burning magnesium is inserted into the jar full of carbon dioxide, it burns brightly and produces white powder of magnesium oxide (MgO) and black carbon powder. This shows carbon dioxide contains carbon.

2Mg (s) + CO2 (g)————————–> 2 MgO (s) + C (s)

Carbon dioxide dissolves in water to form carbonic acid. This gas is mixed in soft drinks at high pressure to bring a sour taste to them.

CO2 (g) + H2O (l)——————————-> H2CO3 (aq)

When carbon dioxide gas is passed into lime water for some time the lime water turns milky white due to the formation of insoluble calcium carbonate.

Ca(OH)2 (aq) + CO2 (g) ————————–> CaCO3 (s) +H2O (l)

Similarly, when this gas is passed into the lime water for a long time then the milky white color disappears due to the formation of soluble calcium bicarbonate.

CaCO3 (s) +H2O (l) +CO2 (g)————————–> Ca (HCO3)2 (aq)

When a few drops of KOH are added inside a test tube filled with CO2 and inverted in water, the water level rises inside the test tube. During this process, KOH absorbs C02 inside the test tube creating low pressure there rushing water into it.

2KOH +CO2 —————————————————————–> K2CO3 + H20

Green plants prepare their food in the form of carbohydrates by the reaction of carbon dioxide absorbed from air and water absorbed by roots in the presence of sunlight trapped by chlorophyll in their leaves.

6CO2 +6H2O ——————–(solar energy +chlorophyll)————-> C6H12O6 +6O2

Carbon dioxide reacts with red hot coke at 900 degrees to form carbon monoxide.

CO2 + C—————–> 2CO

Uses of Carbon dioxide gas

1. Carbon dioxide is dissolved in soft drinks at high pressure.
2. Plants use carbon dioxide as a raw material for the preparation of their food.
3. This gas is used to extinguish the fire. The device used to put off the fire is called a fire extinguisher. Generally, a concentrated solution of sodium bicarbonate is placed inside the cylinder. Concentrated sulphuric acid is placed inside a glass vessel attached to the plunger near the mouth of the extinguisher. When the plunger is jerked, sulphuric acid gets mixed with the sodium bicarbonate, and carbon dioxide is produced which comes out at a very high speed and covers the fire forming a thick blanket. Due to this, there will be a lack of oxygen and the fire gets extinguished.

2 NaHCO3 + H2SO4 ————————————–> Na2SO4 + 2H2O + 2CO2

4. Carbon dioxide is used to prepare dry ice which is used to preserve fruits, vegetables, meat, etc in lower temperatures.

5. Liquid carbon dioxide is used in the purification of sugar by the carbonation process in sugar mills.

6. It is also used to prepare urea (NH2CONH2), washing soda (Na2CO3), and baking soda (NaHCO3).

7. It is used to make carbogen. Carbogen is a mixture of 95% oxygen and 5%carbon dioxide. Carbogen is used to treat patients suffering from pneumonia for their artificial respiration.

8. Green plants use carbon dioxide for photosynthesis.

6CO2 +6H2O ——————–(solar energy +chlorophyll)————-> C6H12O6 +6O2

9. It is used to make bakery products.

Ammonia

Ammonia is found in both free and combined states in nature. This gas is produced when nitrogenous substances decay in the absence of oxygen. Similarly, in combined form, ammonia gas is found in ammonium chloride and ammonium sulfate. Lavoisier prepared this gas by heating the mixture of ammonium chloride and calcium hydroxide.

Fact about ammonia gas

Symbol	Molecular Weight
NH3	17

The molecular weight of ammonia is 17. The molecular weight of oxygen is 32, whereas the molecular weight of nitrogen is 28 and that of carbon dioxide is 44, so this gas is lighter than the air.

Laboratory Preparation of ammonia gas

In the laboratory, ammonia gas is prepared by heating the mixture of ammonium chloride (NH4Cl) and calcium hydroxide (ca(OH)2) in a ratio of 2:1 in a hard glass test tube.

Ammonium Chloride + Calcium Hydroxide————–> calcium Chloride + water + ammonia

2NH4Cl (s) + Ca(OH)2 (s) ———————-> CaCL2 (s) + 2H2O (l) + 2NH3 (g)

Apparatus Required: Hard glass test tube, source of heat, gas jar, stand, lime tower, delivery tube, etc.

Chemicals Required: Ammonium Chloride and Calcium Hydroxide

Method/ Procedure

1. Collect the apparatus and chemicals required for the laboratory preparation of ammonia gas.
2. Mix ammonium chloride and calcium hydroxide in a ratio of 2:1 and put the mixture into a hard glass test tube.
3. Fix a delivery tube in the mouth of the test tube with a rubber cork to make it airtight as shown in the figure. Arrange the hard glass test tube in a slightly inclined position with the help of a stand. Connect the other end of the delivery tube to the lime tower to obtain pure and dry ammonia gas. We can perform the experiment without the lime tower to get impure ammonia.
4. Now heat the mixture gently and observe the formation of ammonia gas.
5. A lime tower filled with Calcium oxide (CaO) is used to obtain the pure and dry ammonia. This gas is quite soluble in water so it is not obtained by the displacement of water. It is collected by the downward displacement of air as it is lighter than the air.

Precautions

1. The mouth of the hard glass test tube should be slightly inclined downward so that the water vapor produced in this process passes to the lime tower through the delivery tube and prevents the hard glass tube from cracking.
2. The mouth of the hard glass test tube should be airtight with the help of the cork.
3. To obtain dry ammonia gas, the should be passed through a lime tower. Since the gas is highly soluble in water, it should not be collected by the displacement of water.

Calcium oxide absorbs moisture from ammonia. So, when ammonia is passed through the lime tower, we get pure and dry ammonia.

Do You Know?

Test of the gas

1. The gas is basic so it changes from moist red litmus to blue.
2. When a glass rod dipped in concentrated hydrochloric acid is brought near the mouth of a gas jar with ammonia, white fumes come out of it.

Properties of ammonia

Physical Properties

1. It is a colorless gas with a strong pungent odor like a rotten egg.
2. It is lighter than the air.
3. This gas is highly soluble in water.
4. It is a basic gas so it changes moist red litmus to blue.
5. Ammonia liquefies at -33 degrees celcius and solidifies at -78 degrees celcius.

Chemical Properties

• This gas is soluble in water. It forms ammonium hydroxide when dissolved in water.
• NH3 (g) + H2O (l) ————————————————————>NH4OH (aq)
• Ammonia reacts with acids to form ammonium salts.
• NH3 (g) + HCl (aq)———————> NH4Cl (aq)
• 2NH3 (g) + H2SO4 (aq) ————–> (NH4)2SO4 (aq)
• Ammonium solution (NH4OH) reacts with acid to form salt and water.
• 2NH4OH (aq) +H2SO4 (aq) ————–>(NH4)2SO4 (aq) + 2H20 (l)
• NH4OH (aq) +HCl (aq)———————>NH4Cl (aq) +H2O (l)
• Ammonia and carbon dioxide react at a high temperature of 1500 degrees Celsius and at high pressure to form urea.
• NH3 (g) +CO2 (g)——pressure+temperature————> NH2-CO-NH2 (s) + H20 (l)
• Urea is an important fertilizer.
• When ammonia burns in the atmosphere of oxygen, it produces nitrogen gas and water.
• 4NH3 (g) + 3O2 (g) ——————> 6H2O (l) + 2N2 (g)
• When a mixture of ammonia and oxygen is passed through the platinum gauze at about 800 degrees Celsius, it produces nitric oxide.
• 4NH3 (g) + 5O2 (g)——-platinum——->6H2O (l) +2NO (g)
• When ammonia is passed through the molten sodium then it forms sodamide and hydrogen gas.
• 2NH3 (g) + 2Na (s)—————-> 2NaNH2 +H2 (g)

Uses of ammonia

1. Ammonia is used to make fertilizers like ammonium sulfate, ammonium nitrate, urea, ammonium phosphate, etc.
2. It is used in the manufacture of nitric acid, plastic, etc.
3. This gas is used to make washing soda.
4. It is used to make medicines of ammonium salts.
5. Ammonia is used to make the blueprints of maps.
6. It is used as a cooling agent in refrigerators.
7. It is used as a cleansing agent to remove the satins of oil, grease, etc.

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