Chapter 4: Carbon and its Compounds

Question 1

Soaps and Detergents:-
Cleansing Action of Soap

Answer 1

When soap is added to water, the soap molecules uniquely orient themselves to form
spherical shape micelles.

The non-polar hydrophobic part or tail of the soap molecules attracts the dirt or oil part of
the fabric, while the polar hydrophilic part or head,(−COO−Na+, remains attracted to water
molecules.

The agitation or scrubbing of the fabric helps the micelles to carry the oil or dirt particles
and detach them from the fibres of the fabric.

Question 2

Hard Water

Answer 2

Hard water contains salts of calcium and magnesium, principally as bicarbonates, chlorides, and sulphates. When soap is added to hard water, calcium and magnesium ions of hard water react with soap forming insoluble curdy white precipitates of calcium and magnesium
salts of fatty acids.

2C17H35COONa + MgCl2 → (C17H35COO)2Mg + 2NaCl

2C17H35COONa + CaCl2 → (C17H35COO)2Ca + 2NaCl

These precipitates stick to the fabric being washed and hence, interfere with the cleaning ability of the soap. Therefore, a lot of soap is wasted if water is hard.

Question 3

Difficulty of Carbon to Form a Stable Ion

Answer 3

To achieve the electronic configuration of nearest noble gas, He, if the carbon atom loses four of its valence electrons, a huge amount of energy is involved. C4+ ion hence formed will be highly unstable due to the presence of six protons and two electrons.
If the carbon atom gains four electrons to achieve the nearest electronic configuration of the noble gas, Ne, C 4− ion will be formed. But again, a huge amount of energy is required.
Moreover, in C 4+ ion it is difficult for 6 protons to hold 10 electrons. Hence, to satisfy its tetravalency, carbon shares all four of its valence electrons and forms covalent bonds.

Question 4

Ionic Bond

Answer 4

Ionic bonding involves the transfer of valence electron/s, primarily between a metal and a nonmetal. The electrostatic attractions between the oppositely charged ions hold the compound together.
Ionic compounds:
1. Are usually crystalline solids (made of ions)
2. Have high melting and boiling points
3. Conduct electricity when melted
4. Are mostly soluble in water and polar solvents

Question 5

Covalent Bonds

Answer 5

A covalent bond is formed when pairs of electrons are shared between two atoms. It is primarily formed between two same nonmetallic atoms or between nonmetallic atoms with similar electronegativity.

Question 6

Lewis Dot Structure

Answer 6

Lewis structures are also known as Lewis dot structures or electron dot structures.
These are basically diagrams with the element’s symbol in the centre. The dots around it represent the valence electrons of the element.

Question 7

Covalent Bonding in H2, N2 and O2