(a) The form of carbon which is known as black lead is graphite.
(b) The form of carbon which is used as a lubricant at high temperature is graphite.
(c) Compounds of carbon with hydrogen alone are called hydrocarbons.
(d) CnH2n is the general formula of alkenehydrocarbons.
(e) Hydrocarbons having the general formula CnH2n−2 are called alkynes.
(f) Ethene and ethyne are examples ofunsaturated hydrocarbons.
(g) Ethyne has two carbon-hydrogen single bonds.
(h) Carbon compounds have usually low melting points and boiling points because they arecovalent in nature.
(i) The property of carbon atoms to form long chains in compounds is called catenation.
(j) The general formula CnH2n for cycloalkanes is the same as that of alkenes.
(k) The IUPAC name of ethylene is ethene.
(l) The IUPAC name of acetylene is ethyne.