Diamond is an allotrope of carbon which was first confirmed by the English chemist Smithson Tennant, who was the first to burn a diamond in air producing carbon dioxide. Thus, according to this statement, option (3) is incorrect.

Carbon is an essential element in all organic compounds.

Lamp black, an amorphous form of carbon, is prepared by heating kerosene oil in a limited supply of air.

All given statements are correct because graphite is an allotrope of carbon, which is a good conductor of heat and electricity and can also be produced artificially.

The common element in all organic compounds, other than H2, is carbon.

Diamond is used as a material for making protective windows in space probes.

Anhydrous ammonia is widely used in industrial refrigeration applications because of its high energy efficiency and low cost.

Graphite is an allotropic form of carbon which can be used as a lubricant.

Organic compounds have low melting points.

A man-made allotropic form of carbon is fullerene.

Carbon compounds have low boiling points because of the weak inter-molecular forces.

Carbon forms so many compounds because carbon readily forms covalent bonds with other carbon atoms.

Unstable covalent bonding is not a characteristic of carbon because it forms stable covalent bonds with other elements.

CaOCO₃ is not an organic compound because carbon is an essential element of all organic compounds.

C – C bond is the most stable covalent bond among all the given bonds.

Diamond is the hardest known substance.

Graphite is a good conductor of electricity due to the presence of mobile (free) electrons.

There are two allotropic forms of carbon. (1) Crystalline form: There are three crystalline forms of carbon: diamond, graphite and bucky ball. (2) Amorphous form: There are various amorphous forms of carbon: coal, coke, charcoal, lampblack, gas carbon, etc.

Graphite is used as a lubricant because it consists of layers which readily slip over one another.

Butane is a major constituent of LPG.