CBSE 2023


In the intricate dance of chemistry, the genesis of salt unfolds when hydrogen ions gracefully yield their place to a metal or ammonium ion within an acid. Simultaneously, a base, engaged in a chemical waltz with an acid, orchestrates the harmonious creation of nothing but water and salt.

Bases, the unsung heroes of household cleansers adept at banishing oil from windows and floors, also find their place of honor in everyday items like soaps, toothpaste, egg whites, dishwashing liquids, and household ammonia.

Introduction to Acids, Bases, and Salts

An acid, distinguished by its tantalizing sourness in water, its alchemy in turning blue litmus into a passionate red, and its knack for neutralizing bases, is a substance of remarkable repute. On the flip side, a base earns its title if its aqueous solution tantalizes the taste buds with bitterness, transforms red litmus into a soothing blue, or adeptly neutralizes acids. And in this intricate tapestry, salt emerges as the neutral protagonist, casting no discernible effect on litmus in its aqueous abode.

Classification of Matter

Breaking down the intricacies of matter involves a multifaceted approach:

  •         Composition:Unveiling the essence through elements, compounds, and mixtures.
  •         State:Capturing the dynamic nature through solids, liquids, and gases.
  •         Solubility:Unraveling the interaction in suspensions, colloids, and solutions.

Further nuances unfold in the realm of mixtures:

  •         Homogeneous and Heterogeneous:The symphony of uniformity and diversity.
  •         Compounds:Navigating the molecular landscape with covalent and ionic distinctions.

For a more profound dive into the Classification of Matter, explore here.

What Is an Acid and a Base?

Ionizable and Non-Ionizable Compounds

Delving into the molecular tapestry, an ionizable compound gracefully transforms when immersed in water or its molten state, effortlessly giving rise to ions. Witness this phenomenon in action with examples like NaCl, HCl, KOH, and more. In contrast, the enigma of non-ionizable compounds lies in their steadfast refusal to dissociate into ions, a trait exemplified by substances such as glucose and acetone.

Acids and Bases

In the realm of acidity, an acid, armed with hydrogen prowess, generously bestows a proton (hydrogen ion) upon another substance. On the opposing front, a base, a versatile entity, gracefully accepts the gift of a hydrogen ion from an acid. The distinctive sour note often identifies acidic substances, offering a sensory cue into the molecular symphony at play.

Arrhenius’ Theory of Acids and Bases

In the intricate dance of chemistry, Arrhenius sheds light on the behavior of acids and bases in aqueous solutions. An Arrhenius acid, when introduced to water, graciously dissociates to yield either H+ or H3O+ ions. On the flip side, an Arrhenius base, in the aqueous realm, gracefully breaks apart to furnish OH− ions.



  •         Hydrochloric acid (HCl)
  •         Sulphuric acid (H2SO4)
  •         Nitric acid (HNO3)


  •         Sodium hydroxide (NaOH)
  •         Potassium hydroxide (KOH)
  •         Calcium hydroxide (Ca(OH)2)

For a deeper dive into Arrhenius’ Theory, explore here.

Bronsted Lowry Theory

Building upon Arrhenius’ insights, the Bronsted Lowry Theory defines acids as H+ ion donors and bases as H+ ion acceptors.


In the reaction: HCl (aq) + NH3 (aq) → NH+4(aq) + Cl− (aq)

  •         In the realm of chemical dynamics, HCl operates as a Bronsted acid, while its counterpart, Cl−, takes on the role of its conjugate acid.
  •         NH3: Bronsted base, and NH+4: its conjugate acid

To unravel more about the Bronsted Lowry Theory, delve here.

Physical Test

Embarking on the realm of identification, two distinct physical tests beckon:

  1. Taste

An acid tantalizes the taste buds with sourness, while a base introduces a bitter note. However, this method is cautioned against due to potential contamination or corrosiveness.

Example: Curd, lemon juice, orange juice, and vinegar’s sour flavors stem from their acidic nature. In contrast, the bitter taste of baking soda exemplifies its basic characteristics.

  1. Impact of Acids and Bases on Indicators

Indicators, responsive chemical substances, undergo changes in physical properties like color or odor when encountering acids or bases.

  1. a) Litmus
  •         Neutral solution: Purple
  •         Acidic solution: Red
  •         Basic solution: Blue

Litmus, available as red and blue strips, undergoes transformative hues when exposed to acids or bases.

Example: An acid turns moist blue litmus paper red, while a base transforms moist red litmus paper to blue.

  1. b) Methyl orange
  •         Neutral solution: Orange
  •         Acidic solution: Red
  •         Basic solution: Yellow
  1. c) Phenolphthalein
  •         Neutral solution: Colourless
  •         Acidic solution: Remains colourless
  •         Basic solution: Pink

Acids and Bases Interactions

When an acid and a base engage in a neutralization reaction, the result is a harmonious transformation into salt and water. This chemical duet follows the standard approach of a double-replacement reaction.

Reactions Unveiled

  1. a) Metals in the Limelight

In the realm of acids and metals, a dance unfolds. Acids, in their general demeanor, gracefully waltz with metals, birthing salt and liberating hydrogen gas. On the flip side, bases maintain a dignified distance, refraining from any intricate metal interaction.


  •         Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen (2HCl + Mg → MgCl2 + H2 (↑))
  1. b) Metal Carbonates and Bicarbonates’ Elegance

As acids encounter metal carbonates or bicarbonates, a spectacular display of effervescence ensues. Carbon dioxide, along with metal salts and water, takes center stage. Lime water, upon contact with the carbon dioxide journey, adorns a milky hue.


  •         Hydrochloric acid + Calcium carbonate → Calcium chloride + Water + Carbon dioxide (2HCl + CaCO3 → CaCl2 + H2O + CO2)
  1. c) Metal Oxides and Hydroxides: The Basic Ensemble

Metal oxides and hydroxides, residing in the realm of bases, gracefully partake in a transformative tango with acids. The outcome: a blend of salt, water, and the warmth of heat.


  •         Sulfuric acid + Magnesium oxide → Magnesium sulfate + Water (H2SO4 + MgO → MgSO4 + H2O)
  1. d) Non-Metal Oxides’ Impact

In a riveting encounter, non-metal oxides, with their acidic nature, join forces with bases, crafting a symphony of salt, water, and the heat of the moment.


  •         Sodium hydroxide + Carbon dioxide → Sodium carbonate + Water (2NaOH + CO2 → Na2CO3 + H2O)
  1. e) The Ever-Present Hydrochloric Acid

A stalwart in the acid realm, hydrochloric acid, in a harmonious dance with its counterpart, sodium hydroxide, elegantly forms salt and water.


  •         Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water (HCl + NaOH → NaCl + H2O)

For a more in-depth exploration of the Properties of Acids and Bases, venture here.

In the aquatic domain, the interplay of acids and bases unfolds as they gracefully disband into their distinctive ions upon introduction to water, facilitating the flow of electricity.

Discerning Base from Alkali

Base: Bases engage in a neutralization dance with acids,

characterized by components such as metal oxides, metal hydroxides, metal

carbonates, and metal bicarbonates. Notably, the majority of bases display

limited solubility in water.

Alkali: An alkali stands as the aqueous manifestation of a

base, predominantly consisting of metallic hydroxides. Dissolving in water, it

elegantly dissociates to bestow the OH− ion. While all alkalis fall under the

category of bases, it’s crucial to note that not every base earns the esteemed

title of alkali.

Hydronium Ion

The formation of a

hydronium ion transpires as a hydrogen ion graciously accepts a lone pair of

electrons from the oxygen atom within a water molecule, forging a coordinate

covalent bond.

Dilution Process

Dilution emerges as a

strategic maneuver to diminish the concentration of a solution by introducing

more solvent, typically water. This process unfolds with notable exothermic

energy release. Notably, when diluting an acid, the prudent approach is to introduce

the acid to water, steering clear of the reverse.

Acids and Bases Potency

In the spectrum of

acidity and basicity, the classification extends to strong and weak categories.

A strong acid or base signifies the complete dissociation of all molecules within

a given amount in water, yielding H+(aq) for acids and OH−(aq) for bases.

Conversely, weak acids or bases exhibit partial dissociation, with only a

fraction of molecules contributing H+(aq) or OH−(aq). Further nuances include

the categorization of dilute acids, featuring fewer H+(aq) ions per unit

volume, and concentrated acids, boasting a higher concentration of H+(aq) ions

per unit volume.

Universal Indicator Insight

The universal indicator,

with a comprehensive pH range spanning from 0 to 14, becomes the beacon in

gauging the acidity or alkalinity of a solution. A neutral solution

harmoniously registers a pH value of 7.

 pH: The Numeric Symphony

The pH value, a testament to the logarithmic magic, is represented as pH = −log10[H+]. In the pristine realms of pure water, where [H+] equals [OH−], both standing at 10−7 mol/L, the pH gracefully settles at a harmonious 7. The pH scale orchestrates a melodious range from 0 to 14, with the eloquent declaration that if pH < 7, it resonates with acidity, and if pH > 7, it sings the song of basicity.

The Dynamics of pH in Daily Life

  1. pH Sensitivity in Life Processes

The sensitivity of plants and animals to pH becomes a defining aspect of their existence. Critical life processes, including food digestion and the orchestration of enzymes and hormones, unfold at specific pH values.

  1. Soil’s pH Tale

For the growth of plants or crops, the soil becomes a narrative dictated by an optimal pH range of 6.5 to 7.0.

  1. Digestive Symphony

Within the digestive system, the process of digestion unfolds in the stomach’s specific pH range of 1.5 to 4. The dance of enzymes, pivotal in food digestion, is influenced by the presence of HCl in the stomach.

  1. Tooth Decay’s pH Prelude

Tooth decay takes center stage when teeth find themselves exposed to an acidic environment of pH 5.5 and below.

  1. pH in the Arsenal of Self-Defense

As a form of self-defense, animals and plants wield acidic substances. Examples include bees and plants like nettles, secreting highly acidic substances, each with its specific pH.

To delve deeper into the intricacies of pH, explore here.

Manufacture of Acids and Bases: Crafting the Chemical Ensemble

  1. a) Nonmetal Oxides as Acid Anhydrides

The marriage of nonmetal oxides with water births acids, exemplified by reactions such as:

  •         SO2(g) + H2O(l) → H2SO3(aq)
  •         SO3(g) + H2O(l) → H2SO4(aq)
  •         4NO2(g) + 2H2O(l) + O2(g) → 4HNO3(aq)
  1. b) Hydrogen and Halogens in Acidic Choreography

The union of hydrogen and halogens unfolds in a dance, as seen in reactions like:

  •         H2(g) + Cl2(g) → 2HCl(g)
  •         HCl(g) + H2O(l) → HCl(aq)
  1. c) Metallic Salts and Sulphuric Acid: A Volatile Symphony

A dynamic interplay involves metallic salts and concentrated sulfuric acid, resulting in reactions like:

  •         2NaCl(aq) + H2SO4(aq) → Na2SO4(aq) + 2HCl(aq)
  •         2KNO3(aq) + H2SO4(aq) → K2SO4(aq) + 2HNO3(aq)
  1. d) Metals and Oxygen’s Ballet: Forming Metallic Oxides

In a ballet with oxygen, metals gracefully form metallic oxides, creating a base:

  •         4Na(s) + O2(g) → 2Na2O(s)
  •         2Mg(s) + O2(g) → 2MgO(s)
  1. e) Metals’ Aquatic Affair: Forming Base or Alkali

The courtship of metals with water results in the formation of base or alkali:

  •         Zn(s) + H2O(steam) → ZnO(s) + H2(g)
  1. f) Metallic Oxides’ Encounter with Water: The Birth of Alkali

In a transformative encounter, a few metallic oxides and water gracefully birth alkali:

  •         Na2O(s) + H2O(l) → 2NaOH(aq)
  1. g) Ammonia and Water: Crafting Ammonium Hydroxide

The synthesis of ammonia and water gives rise to ammonium hydroxide:

  •         NH3(g) + H2O(l) → NH4OH(aq)

Salts: Harmonious Matrimony of Anions and Cations

Within the realm of chemistry, a salt emerges as the artistic fusion of an acid’s anion and a base’s cation.

Illustrative Symphony of Salts

Examples such as KCl, NaNO3, CaSO4, among others, serve as eloquent expressions of salts, meticulously crafted through the alchemy of neutralization reactions between acids and bases.

Epitome of Culinary Harmony: Common Salt

Sodium Chloride (NaCl), known colloquially as common salt, stands as a global culinary maestro, enhancing flavors across the diverse tapestry of cuisines.

The Saline Kinship: Family of Salts

Salts, united by either a common cation or anion, weave a familial tapestry exemplified by members like NaCl, KCl, LiCl.

pH Alchemy of Salts

The pH orchestration of salts follows a nuanced dance:

  •         A salt born of a potent alliance between a strong acid and a strong base assumes a neutral persona (pH = 7, approximately).
  •         Should a salt emerge from the embrace of a weak acid and a strong base, its nature leans towards the basic realm (pH > 7).
  •         Conversely, a salt born of a strong acid and a feeble base carries an acidic demeanor (pH < 7).
  •         The pH identity of a salt, born of both a weak acid and a weak base, unveils itself through the prism of a pH test.

For a deeper exploration of the nuanced world of salts, venture here.

Alchemy Unveiled: Chemicals from Common Salt

Sodium chloride, the paragon of common salt with the molecular formula NaCl, transcends its culinary role. It metamorphoses into an array of compounds:

  1.   Sodium hydroxide or caustic soda.
  2.   Baking soda or sodium hydrogen carbonate, alias sodium bicarbonate.
  3.   Washing soda or sodium carbonate decahydrate.
  4.   Bleaching powder, recognized as calcium hypochlorite.

Sodium Hydroxide: Crafting Caution

The manufacture of sodium hydroxide (NaOH), a potent alkaline force, demands meticulous care. The exothermic reaction, releasing considerable heat, underscores the need for caution to prevent splattering or boiling. NaOH, also known as caustic soda, emerges as a stalwart chemical ally.

Chemical Alchemy Unleashed: NaOH

  •         Chemical formula: NaOH
  •         Alias: Caustic soda

Chlor-alkali Process Unveiled: Brine Electrolysis Ballet

In the intricate dance of the chlor-alkali process, electrolysis of brine, a solution of common salt (NaCl), takes center stage. The anode gracefully releases Cl2, while the cathode contributes the liberation of H2, leaving sodium hydroxide to elegantly persist in the solution.

Bleaching Powder: Water-Soluble Alchemy

Bleaching powder, a versatile entity, dissolves into water, finding its purpose as a bleaching agent in textile industries, an oxidizing force, and a disinfectant across various industrial domains. This alchemical marvel materializes through the interaction of chlorine gas with dry slaked lime (Ca(OH)2), resulting in the synthesis of Ca(OCl)Cl or CaOCl2. When in contact with water, bleaching powder unfurls its bleaching prowess by releasing chlorine.

The Utilitarian Symphony of Bleaching Powder

Bleaching powder steps into various roles:

  1.   It lends its transformative touch to laundry, bleaching clothes with finesse in the textile industry.
  2.   As a robust oxidizing agent, it assumes the mantle of an oxidizer in diverse industrial arenas.
  3.   Its disinfectant capabilities make it a stalwart in the purification of water, transforming it into potable goodness.

Baking Soda’s Alchemical Elegance

Sodium bicarbonate, the enchanting compound known as baking soda, captivates with its chemical formulation NaHCO3. This crystalline substance, often encountered as a fine powder, presents a mildly salty and alkaline taste reminiscent of its counterpart, washing soda (sodium carbonate).

Sodium Bicarbonate Unveiled

  •         Chemical name: Sodium hydrogen carbonate
  •         Chemical formula: NaHCO3

Solvay Symphony: Crafting Sodium Hydrogen Carbonate

In the enchanting ballet of the Solvay process, the birth of sodium hydrogen carbonate unfolds with graceful steps: a. Limestone, adorned in heat, metamorphoses into CaO and CO2 (CaCO3 → CaO + CO2). b. The ethereal dance continues as CO2 pirouettes through a concentrated pas de deux of sodium chloride and ammonia, giving rise to the entrancing partnership of NaHCO3 and NH4Cl (NaCl(aq) + NH3(g) + CO2(g) + H2O(l) → NaHCO3(aq) + NH4Cl(aq)).

The Versatile Artistry of Sodium Hydrogen Carbonate

This chemical virtuoso, also known as baking soda, graces various stages:

  1.   It lends a soothing touch to acidity in the stomach, assuming the role of an antacid for indigestion.
  2.   In the grand theater of washing, it takes center stage as a water softener.

Washing Soda’s Eloquent Presence

Washing soda, a chemical luminary with the regal name sodium carbonate, unveils its magic through the alchemy of the Solvay process. As limestone undergoes the dance of transformation (CaCO3 → CaO + CO2), the ensuing duet of CO2 with a concentrated symphony of sodium chloride and ammonia gives birth to the majestic NaHCO3 and NH4Cl (NaCl(aq) + NH3(g) + CO2(g) + H2O(l) → NaHCO3(aq) + NH4Cl(aq)).

The Radiance of Sodium Carbonate

  1.   It graces the realms of glass, soap, and paper industries with its presence.
  2.   In the backstage of daily chores, it softens the rigidity of water.
  3.   As a domestic virtuoso, it orchestrates the cleansing overture.

Crystalline Tales: Water’s Dance with Salts

Certain salts, with a penchant for elegance, join hands with a precise measure of water in the captivating waltz of crystallisation. This dance, known as crystallisation, unveils structured beauty, be it through precipitation from a solution, freezing, or the rare grace of direct deposition from a gas.

Plaster of Paris: Crafting Healing Artistry

In the artistic realm of sculpting and mending, Plaster of Paris, a white powdery compound born of heated gypsum, graces the stage. The alchemical process involves the metamorphosis of gypsum (CaSO4.2H2O) at 100°C (373K) into CaSO4. ½ H2O and 3/2 H2O, with the embodiment of healing cast for fractures.

Gypsum’s Symphony in Plaster of Paris

  •         Chemical formula: CaSO4. ½ H2O
  •         Alias: Gypsum plaster
  •         Utilitarian Virtuosity: Casts for mending fractures.
  •         Frequently Posed Queries about Acids, Bases, and Salts
  •         Q1In the aqueous realm, what transformative role does an Arrhenius base play? Answer:An Arrhenius base is a compound that orchestrates an increase in the concentration of OH­– ions upon its aqueous sojourn.
  •         Q2Embarking on the pH journey, Solution X unveils a pH of 2, while Solution Y boasts a pH of 1. What clandestine message does this convey about their hydrogen ion congregation contrast? Answer:In the lyrical composition of pH, where lower values echo heightened acidity, Solution Y, adorned with a pH of 1, reveals a grander congregation of hydrogen ions compared to Solution X, adorned with a pH of 2.
  •         Q3In the alchemical dance of dilute hydrochloric acid (HCl) with metals, what gas pirouettes into existence, joining hands with the birth of a corresponding metal salt? Answer:The choreography of acids with metals unfolds a spectacle where dilute hydrochloric acid (HCl) partners with metals, birthing hydrogen gas as a companion to the emergence of the respective metal salt.


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