Question

(a) Differentiate between soap and detergents.
(b) Why pure acetic acid is called glacial acetic acid?
(c) What is covalent bond? Write two properties of covalent compounds.

Answer 1

SOAPS	DETERGENTS
Soaps are the sodium salts of long chain carboxylic acids.	Detergents are the sodium salts of long chain benzene sulfonic acids or alkyl sulfate.
They contain sodium carboxylate (COONa) group.	They contain sodium sulfate (SO3Na) group.
Soaps are prepared from vegetable oils and animal fats.	Detergents are prepared from hydrocarbons of petroleum or coal.
Soaps form a non-soluble precipitate called scum with hard water due to the reaction between calcium and magnesium of the hard water with the soap anions.	Detergents donot form any precipitate even in hard water because the hydrophilic head region of the detergent moiety does not react with the hard water ions.
Soaps react to form scum in hard water, due to which they cannot be used in hard water.	Detergents donot react with hard water, hence can be used with hard water.
Soaps are less effective in hard water.	Detergents are effective, both in hard and soft water.
Soap is biodegradable.	Detergents are non-biodegradable.
Soaps donot pose danger to the ecosystem; they are environmentally safe.	Detergents form thick foams over water bodies which kill the aquatic animals; they are environmentally unsafe.

Table 1: Difference between Soaps and Detergents (Answer to question 'a')

(b) Acetic acid solidifies to ice at the temperature of 16.7 degrees Celsius, which is just less than the room temperature. Due to this solidifying property of acetic acid, it is often known as glacial acetic acid. For acetic acid to form crystals (ice) at cooler temperatures it must be undiluted i.e. contain less than 1% of water, meaning it must be anhydrous.

(c) The bond formed between two atoms by the virtue of sharing a pair of electrons is called as a covalent bond. The forces involved in covalent bonding are electrostatic forces of attraction between the two atoms.

Properties of covalent bonds include:-

1. Solubility; covalent compounds are usually insoluble in polar solvents (water). They are however soluble in non-polar solvents like benzene, toulene, chloroform, hexane etc.

2. Low melting and boiling points; molecules of the covalent compounds are are held by weak forces which can be easily overcome by application of heat. Thus, covalent compounds have low melting and boiling points.