Details and Examples of Inorganic Carbon Compounds

Introduction:

Carbon is one of the most valuable non-metallic elements. Carbon atoms make up the backbone of many important molecules in the human body, including proteins, DNA, RNA, sugars, and fats. The special significance of carbon lies in forming two types of compounds—organic and inorganic compounds. The study of the chemistry of carbon and its compounds is undoubtedly essential for understanding the elements available around us. In contrast to the huge number of organic compounds, the number of inorganic carbon compounds is much less. Oxides, carbides, carbonate and bicarbonates salts, and cyanides are important inorganic compounds.

So far in the last session, we have studied the occurrence of carbon. We have also studied oxides of carbon, i.e., carbon dioxide.

In this session, let us learn more about some of the inorganic compounds of carbon, such as oxides, carbides, carbonate, and bicarbonates.

Carbon Monoxide

Molecular formula: CO

Molecular mass: 28

As the name suggests, carbon monoxide is an oxide of carbon-containing one atom of carbon and one atom of oxygen in its molecule.

Occurrence:

Although carbon monoxide is not a natural component of atmospheric air, it is added to the atmosphere due to the incomplete combustion of fossil fuels, like wood, coal, petrol, etc. Since carbon monoxide is noticed as one of the components of volcanic eruptions. The atmosphere in the volcanic regions contains slightly greater proportions of carbon monoxide. It also occurs in coal gas, tobacco fumes, chimney gases, and automobile exhaust gases (in trace amounts).

Preparation of Carbon Monoxide:

Mainly carbon monoxide is formed when a large amount of carbon and its compound is burnt in limited air or oxygen supply. In other words, carbon monoxide is a product of incomplete burning or combustion of carbon and fuels.

Laboratory Method of Preparation:

Principle: When CO₂ gas is passed over red-hot charcoal, charcoal oxidizes and produces carbon monoxide.

Process: Powder of charcoal is taken in a hard glass test tube, and it is heated. Then, CO₂ gas is passed over this. It oxidizes carbon and turns it into carbon monoxide.

Purification: Carbon monoxide prepared by the above procedure may contain impurities in CO₂ gas. This impurity may be removed by passing the products through a caustic potash solution. (KOH)

Precautions to Take During This Experiment:

1. The charcoal (powdered form) should be kept red hot during the whole chemical reaction.
2. The initial bubble of gas is allowed to pass out, and later the collection of the CO gas is started. (As initial bubbles may contain impurities)
3. Carbon monoxide (CO) is a poisonous gas, the entire preparation process is carried out in a fume chamber.

Carbon monoxide can also be prepared by using oxalic acid and formic acid in the laboratory.

From oxalic acid:  When sulfuric acid is added to the oxalic acid, sulfuric acid absorbs water from oxalic acid and forms carbon monoxide and carbon dioxide.

(Oxalic acid)

From formic acid: When sulfuric acid is added to formic acid, it absorbs water from formic acid, forming carbon monoxide.

(Formic acid)       (Sulfuric acid)                            (carbon monoxide)

Physical properties of Carbon monoxide

1. Carbon monoxide is a colorless, tasteless, neutral gas, but it has a faint odor.
2. It is a highly poisonous gas.
3. It is very sparingly soluble in water.
4. It is a thermally stable gas. (does not decompose even at high temperatures).
5. CO is a combustible gas and a non-supporter of combustion.
6. Boiling point: −192°C.

Chemical Properties of Carbon Monoxide

1. Combustibility:

a.It is combustible and burns in the air with a pale blue flame. A mixture of CO and air burns naturally, resulting in an explosive reaction.

b. Not a supporter of combustion.

2. Reaction with an alkali metal and lime water: It does not react with alkalis as well as with water.

3. Reaction with metals: When CO gas is passed over the finely divided metals, like, nickel, chromium, and iron, metal carbonyls are formed.

4. As a reducing agent:  Carbon monoxide is a strong reducing agent. It reduces the oxides of less active metals to their respective metals and gets oxidized to carbon dioxide.

5. Biochemical process: CO combines with blood’s hemoglobin to form a compound called carboxyhemoglobin. This compound does not allow hemoglobin to absorb or carry oxygen, thus depriving our body cells of oxygen. This causes paralysis of respiratory organs and results in death due to suffocation. This makes CO gas a highly poisonous one.

Uses/Applications of Carbon Monoxide (CO)

1. Since carbon monoxide generates a large amount of heat on combustion, it can also be used as fuel.

Also, carbon monoxide is an important constituent of fuels, like, coal gas, water gas, and producer gas.

2. It can be used in the manufacture of chemicals.

3. Carbon monoxide is used to extract metals like nickel from a mixture of other metals.

4. It is used in the preparation of war gas like phosgene.

Other Inorganic Compounds of Carbon

1. Calcium Carbide( CaC₂):

Calcium carbide is also called calcium acetylide. The molecular formula of calcium carbide is CaC₂.

Preparation: When coke and crushed calcium oxide are heated, calcium carbide is obtained.  

Preparation: When coke and crushed calcium oxide are heated, calcium carbide is obtained.  

2CaO +  6C →  2CaC₂ +  2CO

Physical Properties: It is a greyish-black crystalline solid.

Melting Point: 2160℃

Boiling Point: 2300℃

Chemical Properties: In reaction with water(hydrolysis), it gives acetylene.

(Calcium carbide)      (calcium hydroxide)    (acetylene)

Uses of Calcium Carbide:

1. CaC₂ is used to prepare acetylene gas in the laboratory.
2. Calcium carbide can be used as a dehydrating agent. (removal of water)
3. It can also be used to manufacture graphite and hydrogen.
4. They were used as a ripening agent like ethylene.
5. It is used in bamboo cannons as well as big-bang cannons

2. Silicon Carbide (SiC):

Silicon carbide, also commonly known as carborundum,  is a silicon compound.

Pennsylvanian Edward Acheson discovered the compound known as calcium carbide.

It is the most significant industrial ceramic material. 

Preparation: SiC is prepared by heating silicon dioxide and coke in an electric furnace.

(Silicon dioxide)     (silicon carbide)   (Carbon monoxide)

Physical Properties:

1. It appears as black-grey to green powder, grey solid.
2. SiC is a very hard substance with a high melting point of around  2700^oC.
3. It is insoluble in water.
4. The density of silicon carbide is 3.22 g/cm³.

Chemical Properties of SiC:

When silicon carbide reacts with fused sodium hydroxide in the presence of atmospheric air, it undergoes oxidation to form sodium carbonates and sodium silicates.

(Silicon dioxide)     (Sodium hydroxide)    (Sodium carbonate)   (Sodium silicate)

Uses:

1. Silicon carbide is used as an abrasive.
2. SiC is also used as a grinding stone to cut and sharpen tools.
3. Used in the manufacture of electronic appliances such as light-emitting diodes (LEDs) and detectors

3. Calcium Carbonate (CaCO3):

Calcium carbonate is an inorganic compound. Its molecular formula is CaCO₃. It consists of one atom of carbon, one atom of calcium, and three oxygen atoms in its molecule. It is a commonly found compound on the earth’s crust.  Calcium carbonate is also found in many forms, such as marble, limestone, calcite, etc.

Preparation:

Calcium carbonate is prepared by passing carbon dioxide gas(CO₂) into a solution of calcium hydroxide, and calcium carbonate precipitates out:

(Calcium hydroxide)               ( Calcium carbonate)     (water)

Physical Properties:

1. It is a White Crystalline solid having a melting point of 825^oC

2. The compound calcium carbonate is insoluble in water.

Chemical Properties:

1. Calcium carbonate reacts with strong acids releasing carbon dioxide gas.

2. It reacts with water to form soluble calcium bicarbonate.

Uses of Calcium Carbonate:

1. It is mostly used as a dietary supplement when the amount of calcium taken in the diet is insufficient.
2. The major calcium carbonate applications are in building materials, ceramic tiles, and blackboard chalk.
3. It is used to manufacture paints, paper, plastics, etc.
4. It is used as the base material for medicinal tablets.

Comparative Study of Sodium Carbonate (Na₂CO₃) and Sodium Bicarbonate (NaHCO₃)

Sodium carbonate is also termed washing soda, and it is a sodium salt of carbonic acid. 

The molecular formula of sodium carbonate is Na₂CO_3.

It is commonly mentioned as soda ash because it was originally obtained from burnt seaweed’s ashes.

Sodium Bicarbonate or Sodium Hydrogen Carbonate (NaHCO₃)

The chemical name of washing soda is sodium hydrogen carbonate or sodium bicarbonate.

Its molecular formula is NaHCO_3.

Summary

• Carbon is one of the most important non-metal elements.
• Carbon compounds are mainly classified into two types, namely, inorganic carbon compounds and organic compounds.
• Oxides, carbides, carbonate and bicarbonates salts and cyanides are important inorganic compounds.
• Carbon monoxide is a colorless, tasteless, and neutral gas, but it has a faint odour.
• Calcium carbide is also called calcium acetylide. CaC2 is used to prepare acetylene gas in the laboratory, used as a dehydrating agent.
• Silicon carbide, also commonly known as carborundum, is a silicon compound.
• Calcium carbonate is found in many forms, such as marble, limestone, and calcite.
• The other inorganic compounds of carbon are sodium carbonate and sodium bicarbonate.