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 (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.

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)

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)

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   

Salts are of three kinds based on 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)

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.

Acids, bases, and salts are fundamental chemical substances that play vital roles in chemistry, biology, industry, and daily life. These compounds differ in their properties, composition, reactions, and uses. Understanding them is crucial for grasping many chemical processes in nature and laboratories.

Acids are substances that donate hydrogen ions (H⁺) when dissolved in water. They usually taste sour and can be corrosive.

• Sour in taste (e.g., citric acid in lemon).
• Turn blue litmus paper red.
• React with metals like zinc and magnesium to release hydrogen gas.
• Have a pH less than 7.
• Conduct electricity in aqueous solutions due to the presence of ions.

• Organic Acids: Found in plants and animals (e.g., acetic acid, citric acid).
• Mineral Acids: Strong acids used in laboratories and industries (e.g., hydrochloric acid, sulfuric acid, nitric acid).

• Hydrochloric acid (HCl) – Found in the stomach.
• Sulfuric acid (H₂SO₄) – Used in car batteries.
• Nitric acid (HNO₃) – Used in fertilizers and explosives.
• Acetic acid (CH₃COOH) – Found in vinegar.
• Citric acid – Found in citrus fruits.

Bases are substances that accept hydrogen ions or release hydroxide ions (OH⁻) in solution. They usually taste bitter and feel slippery.

• Bitter taste and slippery to touch.
• Turn red litmus paper blue.
• React with acids to form salt and water (neutralization).
• Have a pH greater than 7.
• Conduct electricity in aqueous solutions.

• Strong Bases: Completely dissociate in water (e.g., sodium hydroxide).
• Weak Bases: Partially dissociate in water (e.g., ammonia).

• Sodium hydroxide (NaOH) – Used in soap making.
• Potassium hydroxide (KOH) – Used in batteries.
• Calcium hydroxide (Ca(OH)₂) – Used in whitewashing.
• Ammonium hydroxide (NH₄OH) – Found in household cleaners.

Salts are ionic compounds formed when an acid reacts with a base. This reaction is called neutralization. Salts consist of a positive ion (cation) from a base and a negative ion (anion) from an acid.

• Generally solid and crystalline at room temperature.
• Can be soluble or insoluble in water.
• Have no effect on litmus paper in most cases.
• Have high melting and boiling points.

• Normal Salts: Formed when all the hydrogen atoms of an acid are replaced by metal ions.
• Acid Salts: Contain replaceable hydrogen atoms (e.g., sodium bisulfate).
• Basic Salts: Contain hydroxide ions (e.g., basic lead carbonate).
• Double Salts: Formed by the combination of two different salts (e.g., Mohr’s salt).
• Complex Salts: Contain a complex ion (e.g., potassium ferrocyanide).

• Sodium chloride (NaCl) – Common table salt.
• Calcium sulfate (CaSO₄) – Used in plaster of Paris.
• Sodium bicarbonate (NaHCO₃) – Used in baking soda.
• Ammonium nitrate (NH₄NO₃) – Used in fertilizers.
• Copper sulfate (CuSO₄) – Used in agriculture and electroplating.

A neutralization reaction occurs when an acid and a base react to form salt and water. This is an exothermic reaction and is widely used in industries and medicine.

General reaction: Acid + Base → Salt + Water

Example: HCl + NaOH → NaCl + H₂O

The pH scale measures the concentration of hydrogen ions in a solution and ranges from 0 to 14.

• pH < 7: Acidic solution
• pH = 7: Neutral solution
• pH > 7: Basic solution

Universal indicators and pH papers are used to determine the pH of a substance.

• Used in digestion (HCl in stomach).
• Citric acid and acetic acid in cooking.
• Sulfuric acid in car batteries.

• Used in cleaning products.
• Sodium hydroxide used in soap making.
• Calcium hydroxide for whitewashing.

• Sodium chloride as food seasoning.
• Ammonium nitrate in fertilizers.
• Baking soda used in cooking and medicine.

• **Acids** like sulfuric acid are used in fertilizers, petrochemicals, and metal processing.
• **Bases** are used in soap and paper industries.
• **Salts** are used in electroplating, water treatment, and preservation.

• Always handle acids and bases with gloves and goggles.
• Do not taste or directly inhale chemical substances.
• In case of contact, wash with plenty of water and seek medical attention.

Acids, bases, and salts are essential to many chemical processes, both in nature and in industry. Their unique properties, reactions, and wide-ranging uses make them central to the study of chemistry. A strong understanding of these substances provides the foundation for further studies in science and practical applications in everyday life.