ACIDS, BASES AND SALTS

Acids, Bases and Salts are non- separable components of human life. They affect our life as much as they affect chemistry. Acids and bases can be identified as they have different taste. Acid tastes sour whereas base tastes bitter.

Acid and Bases testing in laboratories

Acid (or acidic solution) turns Blue litmus Red.

Base (or alkaline solution) turns Red litmus Blue.

Some substance whose odor changes in Acidic or Basic media are called Olfactory indicators. E.g. onion, clove oil, vanilla extract etc.

Neutralization Reaction

The Reaction between acid and base to yield salt and water is known as a neutralization reaction.

Base + Acid → Salt + Water

E.g. NaOH (aq) + HCl (aq) → NaCl (aq) + H₂O (l)

Common property of all Acids and Bases

The cation present in acids is H⁺, this suggest that acids produce hydrogen ions, H⁺ (aq), in solution.

E.g. HCl + H₂O → H₃O⁺ + Cl^-

The anions present in bases in OH^-, this suggest that bases produce hydroxide ion in solution.

E.g. KOH (s) + H₂O → K⁺ (aq) + OH^- (aq)

Strength of Acid and Base solutions

A scale of measuring hydrogen ion concentration in a solution is called pH scale. pH scale can measure pH from 0 (very acidic) to 14 (very alkaline).

Higher the hydronium ion concentration lower is pH value.

pH of solutions,

Acidic : 0 to <7
Neutral : 7
Alkaline : >7 to 14

pH of Salts

Salts are of three kinds based on the the pH which is determined by the kind of acid and base responsible for the formation of salt,

Neutral Salt – pH 7 (Salt of Strong Acid and Strong Base)
Acidic Salt – pH less than 7 (Salt of Strong Acid and Weak Base)
Basic Salt – pH more than 7 (Salt of Weak Acid and Strong Base)

Common Salt

Salt that we use in food is the Common salt. Chemical formula for common salt is NaCl.

Seawater contains many salts dissolved in it, sodium chloride is separated from these salts.

Deposits of solid salt are found. These large crystals are called rock salt.