Which is the most thermodynamically stable form of carbon?

• Carbon black

• Graphene

• Graphite

• Diamond

Carborundum is the commercial name of

• B₄C

• SiO₂

• SiC

• Al₂O₃

A gaseous carbon compound is soluble in dilute HCl. The solution on treating with NaNO₂ gives off nitrogen leaving behind a solution which smells of wood spirit. The carbon compound is

• HCHO

• CO

• C₂H₅NH₂

• CH₃NH₂

A signature, written in carbon pencil weighs 1 mg. What are the number of carbon atoms mpresent in the signature?

• 5.02 × 10²³

• 5.02 × 10²⁰

• 6.02 × 10²⁰

• 0.502 × 10²⁰

65.

Activated charcoal is used to remove colouring matter from pure substances. It works by

• oxidation

• reduction 

• bleaching

• adsorption

Graphite is a soft solid lubricant extremely difficult to melt. The reason for this anomalous behaviour is that graphite

• is an allotropic form of carbon

• ia a non-crystalline substance

• has carbon atoms arranged in large plates of ring of strongly bond carbon atoms with weak interplate bonds

• has molecules of variable molecular masses like polymers

Which one of the following has maximum number of atoms of oxygen?

• 2 gm of carbon monoxide

• 2gm of carbon dioxide

• 2 gm of sulphur dioxide

• 2 gm of water

Which one of the following is a molecular crystal?

• Rock salt

• Quartz

• Dry ice

• Diamond

Carbon cannot reduce Fe₂O₃ to Fe at a temperature below 983 K because

• free energy change for the formation of CO is more negative than that of Fe₂O₃

• CO is thermodynamically more stable than Fe₂O₃

• carbon has higher affinity towards oxygen than iron

• iron has higher affinity towards oxygen than carbon

Which one of the following is a covalent crystal?

• Rock salt

• Ice

• Quartz

• Dry ice