Carbon and its Compounds
This chapter explains why carbon forms the basis of a huge number of compounds due to its tetravalency and catenation, covers covalent bonding, homologous series, and the chemistry of soaps and detergents.
A covalent bond is formed by the mutual sharing of electrons between two atoms, each contributing at least one electron to the shared pair, so that both atoms attain a stable noble gas electronic configuration.
Carbon forms a very large number of compounds because of two special properties: catenation (the ability of carbon atoms to bond with other carbon atoms to form long chains, branched chains or rings) and tetravalency (carbon has 4 valence electrons, allowing it to bond with four other atoms of carbon or other elements).
Q. Why does carbon form compounds mainly by covalent bonding?
Carbon has 4 electrons in its outermost shell. It cannot gain or lose 4 electrons easily to form ions, because gaining would require too much energy and losing would need very high ionisation energy. Instead, it shares its electrons with other atoms to form strong covalent bonds.
A homologous series is a group of organic compounds having the same general formula, similar chemical properties, and each successive member differing from the previous one by a -CH2- unit.
Q. What happens when ethanol reacts with sodium metal?
Ethanol reacts with sodium to form sodium ethoxide and hydrogen gas is evolved: 2Na + 2CH3CH2OH -> 2CH3CH2ONa + H2.
Which functional group is present in CH3COOH (acetic acid)?
Correct answer: (C) Carboxylic acid group (-COOH)
Soap molecules form a _______ around oil/dirt particles in water, which helps in cleaning.
Micelle
Diamond and graphite are both made of pure carbon but have different physical properties.
True — diamond and graphite are allotropes of carbon. Diamond has a rigid tetrahedral 3D structure making it extremely hard, while graphite has a layered hexagonal structure making it soft and a good conductor of electricity.
Write the structural formula and molecular formula of the fourth member of the alkane homologous series (CnH2n+2).
The fourth member of the alkane series has n = 4, so the molecular formula is C4H10 (butane), with structural formula CH3-CH2-CH2-CH3.