General Science : Acids, Bases and Salts

By Asha Gupta|Updated : September 4th, 2021

Complete coverage of syllabus is a very important aspect for any competitive examination but before that important subject and their concept must be covered thoroughly. In this article, we are going to discuss General Science: Acids, Bases and Salts

ACIDS, BASES, AND SALTS

Acids:

An acid is a substance that furnishes hydrogen ions (H+) when dissolved in water. For example, in its aqueous solution, hydrochloric HC1 (aq) dissociates as: HC1 (aq) H+(aq) + Cl-(aq)

Some examples of acids are:

  1. Hydrochloric acid (HC1) in gastric juice.
  2. Carbonic acid (H2CO3) in soft drinks.
  3. Ascorbic acid (vitamin C) in lemon and many fruits.
  4. The citric acid in oranges and lemons.
  5. The acetic acid in vinegar.
  6. The tannic acid in tea.
  7. Nitric acid (HNO3) is used in laboratories.
  8. Sulphuric acid (H2SO4) is used in laboratories.

Strong and Weak Acid:

Strong Acid:

The acids that completely dissociate in water are called strong acids. Nitric acid completely dissociates in water HNO3(aq) H+ (aq) NO - (aq) There are only seven strong acids:

  • HCI-Hydrochloric Acid
  • HBr-Hydrobromic Acid
  • HI-Hydroiodic Acid
  • HCIO-Perchloric Acid
  • HCIO3-Chloric Acid
  • H2SO4-Sulphuric Acid
  • HNO3-Nitric Acid

Weak Acids:

The acids that dissociate partially in water are called weak acids. All organic acids like acetic acid and some inorganic acids are weak acids.

Since their dissociation is only partial, it is depicted by double half arrows.

HF(aq) H+(aq) + F-(aq)

The double arrows indicates here that:

(i) the aqueous solution of hydrofluoric acid not only contains H+(aq) and F-(aq) ions but also the dissociated acid HF(aq). (ii) there is an equilibrium between the dissociated acid HF (aq) and the ions furnished by it, H+(aq) and F-(aq)

Examples:

  • CH3COOH Ethanoic (acetic) acid
  • HF Hydrofluoric acid

Bases:

A base is a substance that furnishes hydroxide ions (HO-) when dissolved in water. For example, sodium hydroxide NaOH (aq),

In its aqueous solutions dissociates as:

NaOH (aq) Na+(aq) + OH-(aq)

Strong Base and Weak Base:

Strong Bases:

These bases are completely dissociated in water to form the cation and hydroxide ion (OH).

KOH(aq) K+(aq) + OH-(aq)

There are only eight strong bases. These are the hydroxides of the elements of the Groups 1 and 2 of the periodic table:

  1. LiOH Lithium hydroxide.
  2. NaOH Sodium hydroxide
  3. KOH Potassium hydroxide

Weak Bases:

Weak bases do not furnish OH- ions by dissociation. They react with water (OW). to furnish OH— ions.

NH3(g)+H2O(I) NH4OH NH4OH(aq) NH+ (aq) + OH-(aq)

Examples of weak bases:

  1. NH4OH
  2. Cu(OH)2
  3. Cr(OH)3
  4. Zn(OH)2

Difference between Acid and Base

Nature

Acids

Bases

Taste

Sour

Bitter

Solution

Corrosive to metals

Slippery in nature

Litmus test

Blue to red

Red to blue

Neutralization

After adding base

After adding base

Phenolphthalein Test

Colourless

Pink

Methyl orange

Red

Yellow

Salts:

Salts are ionic compounds made of a cation other than an H+ ion and an anion other than an OH- ion.

Formation of salts: Salts are formed in many reactions involving acids and bases.

  1. By Neutralization of acids and bases: Salts are the product (besides water) of a neutralization reaction.

For example, Base Acid Salt Water

NaOH + HC1 NaC1 + H2O

  1. By action of acids on metals: In a reaction between an acid and a metal, salt is produced along with hydrogen, Metal Acid Salt Hydrogen.

Zn + H2SO4 ZnSO4 + H

  1. By action of acids on metal: Carbonates and hydrogen carbonates Salts are produced in reactions between acids and metal carbonates and hydrogen carbonates (bicarbonates) along with water and carbon dioxide.

CaCO3 + 2HC1 CaC12 + H2O + CO

Type of salt and the nature of its aqueous solution:

Salt of Acid

Salt of Base

Nature of Salt Solution

pH (at 25°C)

Strong

Strong

Neutral

7

Weak

Strong

Basic

>7

Strong

Weak

Acidic

<7

Weak

Weak

More information required

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Posted by:

Asha GuptaAsha GuptaMember since Mar 2021
Associate Content Developer - AE/JE Non-technical
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AE & JERVUNLUPSSSCSDEPSPCLPPSCSSC JEGPSCTNPSCAAIDFCCILUPRVUNLPSPCLOthersPracticeMock TestCourse
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