pH is measured using pH paper, pH meters, or indicators that change colour depending on the acidity or basicity of the solution.

What is the difference between a strong acid and a weak acid?

A strong acid completely dissociates in water, releasing all its hydrogen ions, whereas a weak acid only partially dissociates.

Can bases be dangerous?

Yes, strong bases can be corrosive and harmful to skin and tissues, similar to strong acids.

Acids and Bases: Properties, Brønsted-Lowry Theory, and Lewis Concept

Properties of Acids and Bases: This article is a foundational guide for students to understand acids and bases along with their properties. Here you will learn about the acid and base definition, pH, properties, theories, examples, and uses.

ByAtul Rawal

Jul 25, 2024, 18:06 IST

Acids and Bases: Properties, Brønsted-Lowry Theory, Examples, Uses, Lewis and Arrhenius Concept

Acids and Bases: We have heard these terms in our day-to-day lives but hardly thought of the science behind them. Well, now you can understand these terms easily through this explainer. This detailed article on acids and bases will discuss their definitions, properties, uses, theories, and examples. Read to know more.

Acids and Bases Definition

Acids and bases are two fundamental categories of chemical substances that have distinct properties and reactions. An acid is a substance that donates hydrogen ions (H⁺) in a solution, while a base is a substance that accepts hydrogen ions or donates hydroxide ions (OH⁻) in a solution.

pH of Acids and Bases

The pH scale measures the acidity or basicity of a solution. It ranges from 0 to 14, with 7 being neutral. A pH less than 7 indicates an acidic solution, while a pH greater than 7 indicates a basic (alkaline) solution.

Properties of Acids and Bases

Properties of Acids:

Taste sour
Turn blue litmus paper red
React with metals to produce hydrogen gas
Conduct electricity in solution
Corrosive to metals and skin

Properties of Bases:

Taste bitter
Feel slippery
Turn red litmus paper blue
Do not react with metals in the same way acids do
Conduct electricity in solution

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Theories of Acids and Bases

Several theories have been developed to explain the behaviour of acids and bases. The most notable theories include the Arrhenius concept, the Brønsted-Lowry theory, and the Lewis concept.

Arrhenius Concept of Acids and Bases

According to the Arrhenius concept:

Acid: A substance that increases the concentration of hydrogen ions (H⁺) when dissolved in water. For example, HCl → H⁺ + Cl⁻.
Base: A substance that increases the concentration of hydroxide ions (OH⁻) when dissolved in water. For example, NaOH → Na⁺ + OH⁻.

Brønsted-Lowry Theory of Acids and Bases

According to the Brønsted-Lowry theory:

Acid: A substance that donates a proton (H⁺). For example, HCl + H₂O → H₃O⁺ + Cl⁻
Base: A substance that accepts a proton (H⁺). For example, NH₃ + H₂O → NH₄⁺ + OH⁻

Conjugate Acids and Bases

In the Brønsted-Lowry theory, each acid has a conjugate base formed when the acid donates a proton, and each base has a conjugate acid formed when the base accepts a proton.

Conjugate Acid: The species formed after a base gains a proton.
Conjugate Base: The species formed after an acid loses a proton.

Lewis Concept of Acids and Bases

According to the Lewis concept:

Acid: A substance that accepts an electron pair.
Base: A substance that donates an electron pair.

For example, in the reaction between ammonia (NH₃) and boron trifluoride (BF₃):

NH₃ (Lewis base) donates an electron pair to BF₃ (Lewis acid), forming a coordinate covalent bond.

Uses of Acids and Bases

Uses of Acids:

Hydrochloric Acid (HCl): Used in stomach digestion, cleaning metal surfaces, and manufacturing.
Sulphuric Acid (H₂SO₄): Used in car batteries, fertilisers, and chemical manufacturing.
Acetic Acid (CH₃COOH): Used in food preservation (vinegar) and as a chemical reagent.

Uses of Bases:

Sodium Hydroxide (NaOH): Used in soap making, paper production, and drain cleaning.
Calcium Hydroxide (Ca(OH)₂): Used in construction (plaster), sewage treatment, and agriculture.
Ammonium Hydroxide (NH₄OH): Used in household cleaners and fertilisers.

Examples of Acids and Bases

Get here 10 examples of acid and base that are generally asked in question papers. This table provides a clear overview of various common acids and bases, their chemical formulas, and their typical uses or occurrences.

Acid	Formula	Common Use/Occurrence	Base	Formula	Common Use/Occurrence
Hydrochloric Acid	HCl	Used in stomach digestion, cleaning metals	Sodium Hydroxide	NaOH	Used in soap making, drain cleaner
Sulphuric Acid	H₂SO₄	Used in car batteries, fertilisers	Calcium Hydroxide	Ca(OH)₂	Used in construction (plaster), agriculture
Acetic Acid	CH₃COOH	Found in vinegar, food preservation	Ammonium Hydroxide	NH₄OH	Used in household cleaners, fertilisers
Nitric Acid	HNO₃	Used in fertilisers, explosives	Potassium Hydroxide	KOH	Used in soap making, electrolyte in batteries
Phosphoric Acid	H₃PO₄	Used in soft drinks, rust removal	Magnesium Hydroxide	Mg(OH)₂	Used in antacids, laxatives
Carbonic Acid	H₂CO₃	Found in carbonated beverages	Aluminium Hydroxide	Al(OH)₃	Used in water purification, antacids
Citric Acid	C₆H₈O₇	Found in citrus fruits, used as a preservative	Lithium Hydroxide	LiOH	Used in battery electrolytes, air purification
Lactic Acid	C₃H₆O₃	Found in sour milk, used in food industry	Barium Hydroxide	Ba(OH)₂	Used in analytical chemistry
Formic Acid	HCOOH	Found in ant venom, used in leather production	Zinc Hydroxide	Zn(OH)₂	Used in medicine, manufacturing processes
Tartaric Acid	C₄H₆O₆	Used in baking powder, wine production	Strontium Hydroxide	Sr(OH)₂	Used in sugar refining, water treatment