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Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams PDF Download

A wide variety of materials consists essentially of elements and compounds having different characteristics that exist around us. Some of them are sour, some are bitter, while some are salty in taste. 

Example: Sour and bitter tastes of food are due to acids and bases, respectively, present in them.

Acids react with bases to produce salt whose properties are different from acid and base.

Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams

What are Acids?

The term "acid" is derived from the latin word "acidus" meaning sour to taste. Acids are defined as the one which produces hydrogen/Hydroxyl ions in water.
Example: Sulphuric Acid(H2SO4), Hydrochloric Acid (HCl) etc.

Properties of Acids:

  • Acids are sour in taste.
  • Acids turn blue litmus to red. This is used as a confirmation test for the presence of acid.
  • Acidic solutions can conduct electricity because they dissociate into ions which conduct electricity. 
  • Produce hydrogen(H+)/hydroxyl(H3O+) ions in water.
  • When acids react with metals, Hydrogen gas is evolved.
  • Acids are corrosive in nature.

According to Arrhenius: Those substances which give hydronium ion(H3O+) or Hion in their aqueous solution are called acids.

Note: Due to the corrosive nature acids are stored in glass and ceramic bottles.

Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams


Question for Overview: Acids & Bases - 1
Try yourself: Which one will change from blue litmus to red?
View Solution

Chemical Properties of Acids 

  1. The Reaction of Acid with Metal
    Metal  +  Acid → Hydrogen gas  +  Salt
    Mg + H2SO4 → H2 + MgSO4
  2. The Reaction of Acid with Metal Carbonates
    Acids react with metal carbonates to form salt + water + CO2 gas↑:
    Na2CO3(s) + 2 HCl (aq) → 2NaCl(aq) + H2O (l) + CO2(g)The Reaction of Acid with Bicarbonates
    Acids react with metal bicarbonates to form salt + water + CO2 gas :
    NaHCO3 + HCl → NaCl + H2O + CO2The Reaction of Acids with Base (Neutralization reaction)
    Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank ExamsNeutralisation Reaction
    Neutralisation Reaction

  3. The Reaction of Acid with Metal Oxide
    Salt and water are formed as metal oxides are basic in nature:
    Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams

Question for Overview: Acids & Bases - 1
Try yourself:When an acid reacts with a metal, which one of the following gas is usually liberated?
 
View Solution

Question for Overview: Acids & Bases - 1
Try yourself:What would be the correct balanced chemical equation for neutralization ?
View Solution

Classification of Acids


➢ On the Basis of Occurrence
(a) Mineral Acids (Inorganic Acids)
The acids which are usually obtained from minerals are known as Inorganic acids.
Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams

Do You Know? 
Aqua regia is also known as royal water because it can dissolve less reactive metals into it.

Example: Gold(Au) and Platinum(Pt)

Question for Overview: Acids & Bases - 1
Try yourself:Which of the following is used for dissolution of gold?
View Solution

(b) Organic Acids: Acids which are derived from plants and animals are known as Organic Acids. 
Example: Citric Acid from fruit

Table: Organic Acids
Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams


➢ On the Basis of their Basicity
The basicity of an acid is the number of replaceable hydrogen atoms present in a molecule that can be produced by the complete ionisation of one molecule of that acid in an aqueous solution.

OR 

The basicity of an acid is determined by the number of hydronium ions (H3O+/H+(aq) produced per molecule of acid on ionisation.
(a) Monobasic Acids
The acid on complete ionisation produces one hydronium ion in aqueous solution.
Example:

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

  • Acetic acid (CH3COOH)

  • Formic acid (HCOOH)

Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams
(b) Dibasic Acid
The acid on complete ionization produces two hydronium ions per molecule of acid in aqueous solution.
Example:
  • Sulphuric acid (H2SO4)
  • Carbonic acid (H2CO3)

Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams

(c) Tribasic Acid
The acid on complete ionisation produces three hydronium ions per molecule of acid in aqueous solution.
Example:

  • Phosphoric acid (H3PO4)

Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams

➢ Classification on the Basis of their Strength
(a) Strong Acid
The acid which undergoes complete ionisation in an aqueous solution is known as strong acids.
Example:

Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank ExamsOverview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams(b) Weak Acid
The acid which undergoes partial or incomplete ionization in aqueous solution is known as weak acids.
Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank ExamsExample: 

  • Formic acid (HCOOH)
  • Oxalic acid (COOH)2
  • Carbonic acid (H2CO3)
  • Phosphoric acid (H3PO4)

➢ Classification on the Basis of Concentration of the Acid
(a) Concentrated Acid
The acids which contain a very small amount of water is called a concentrated acid.
(b) Dilute Acid

  • The acid which contains more amount of water is called a dilute acid. "Strength of an acid does not depend upon the concentration of an acid."

Important Fact
Aqua - Regia - Aqua regia is a mixture of (3 part HCl & 1 part HNO3) which dissolves even noble metals like Au(Gold), Pt(Platinum).

  • Strength of an Acid ∝ Concentration of hydronium ion

Dilution

Process of DilutionProcess of Dilution

Dilution of Acid
  • Dilution is the process of reducing the concentration of a solution by adding more solvent (usually water) to it.
  • It is a highly exothermic process.
  • To dilute acid, the acid must be added to water and not the other way round.

Question for Overview: Acids & Bases - 1
Try yourself:Which of the following acids is used as a food preservative?
View Solution


What are Bases?

Substances with a bitter taste and give a soapy touch are known as bases.

Example:

  • Sodium hydroxide (NaOH)
  • Zinc oxide (ZnO)
  • Copper oxide (CuO)
  • Calcium hydroxide [Ca(OH)2]
  • Magnesium hydroxide [Mg(OH)2]
  • Aluminium hydroxide [Al(OH)3]

Properties of Bases:

  • Bases produce hydroxide ions [OH] in H2O.
  • Water-soluble bases are called alkalies.
  • Bases are bitter in taste.
  • Bases turn Red Litmus blue.
  • Bases act as electrolytes in Solution.
  • Bases neutralize solutions containing H+ ions.
  • Bases have a slippery, ‘soapy’ feel.
  • Bases dissolve fatty material.
  • Strong bases are corrosive in nature.
    Example: NaOH, KOH

According to Arrhenius
"Those substances which give hydroxide or hydroxyl ion (OH-) in their aqueous solution" are called bases.

NaOH(aq.) → Na+(aq) + OH-(aq)
KOH(aq.) → K+(aq) + OH-(aq)

  • The compounds which are either metallic oxides or metallic hydroxides combine with acids to form salts and water only:
    CuO + 2HCl  →  CuCl2  +  H2O
    Base     Acid        Salt       Water
    NaOH  + HCl  →  NaCl  +  H2O
    Base       Acid         Salt       Water
    Mg (OH)2 + H2SO4 → MgSO4  + 2H2O
    Base            Acid          Salt          Water

Question for Overview: Acids & Bases - 1
Try yourself:What is the effect of the base on red litmus paper?
View Solution


What are Alkalis?

Bases that completely dissolve in water are called alkalis.
Examples:  KOH, NaOH, Ca(OH)2

All the alkalis are bases but all bases are not alkalis.

Examples: [Fe(OH)3] ferric hydroxide and cupric hydroxide [Cu(OH)2] are base, but not an alkali.

Chemical Properties of Bases


1. Reaction with Metals

  • Base reacts with active metals and produce hydrogen gas.
    Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams

2. Reaction with Acids (Neutralization Reaction)

  • Base reacts with acids to form salts and water.
    Example: KOH + HCl → KCl + H2O

3. Reaction with Non-metallic Oxides

  • Base reacts with non-metallic oxides to form salts and water.
  • Base + Non metallic → salt + water
    Ca(OH)2 + CO2 → CaCO3 + H2O
    NaOH + CO2 → Na2CO3 + H2O
    Mg(OH)2 + CO2 → MgCO3 + H2O

Classification of Bases


➢  Classification on the basis of their Strength
(a) Strong alkalis or bases

  • The alkalis or bases which undergo almost complete ionisation in aqueous solution are known as strong alkalis or bases.
    Example:
    Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams

(b) Weak alkalis or bases

  • The alkalis or bases which undergo only partial ionisation in aqueous solution are known as weak alkalis or Bases.
    Example:
    Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams

➢ Classification on the basis of their Concentration
(a) Concentrated Base or Alkali

  • The bases or alkalis which contain a very small amount of water is called concentrated bases or alkalis.

(b) Dilute Base

  • The bases or alkali which contain more amount of water is called a dilute bases or alkalis
➢ Classification on the basis of their Acidity
  • The acidity of a base is determined by the number of hydroxyl (OH-) ions produced per molecule of a Base or Alkali on complete dissociation in water. 
"or"
  • The "number of hydrogen ions of an acid with which a molecule of that alkali or base react to produce salt and water is known as the acidity of an alkali or Base".

(a) Mono Acidic Bases or Alkali

  • The base or alkali on complete ionisation produces one hydroxyl (OH_) ion per molecule of the base in an aqueous solution.
    Example:
    NaOH (aq.) → Na+ (aq) + OH- (aq)

                                         Hydroxyl ion
    KOH(aq.) → K+ (aq) + OH- (aq)

                                       Hydroxyl ion

(b) Diacidic Bases (or alkalis)

  • The base or alkali on complete ionization produces two hydroxyl ion (OH-) per molecule of the base in an aqueous solution.
    Example:
    (i) Diacidic Bases
    Ca(OH)2(aq.) → Ca2+(aq.) + 2OH-(aq.)
    Mg(OH)2(aq.) → Mg2+(aq.) + 2OH-(aq.)
    (ii) Ferrous hydroxide [Fe(OH)2] and copper hydroxide [Cu(OH)2]
    Fe(OH)2(aq.) → Fe2+ + 2OH-(aq.)
    Fe+2(OH)2- + 2H+Cl-(aq.) → FeCl2 + 2H2O

(c) Tri Acidic Bases

  • The base or alkali on complete ionization produces three hydroxyl ion (OH)-  per molecule of the base in aqueous solution.
    Example: Aluminium hydroxide [Al(OH)3], Ferric hydroxide [Fe(OH)3]
    Al(OH)3(aq.) → Al3+(aq.) + 3OH-(aq.)
    Al3+(OH)3- + 3HCl(aq.) → AlCl3 + 3H2O

Table: Uses of Bases

Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams

Table: Comparison Between Properties of Acids & Bases

Overview: Acids & Bases - 1 | General Awareness & Knowledge - Bank Exams


Frequently Asked Questions

Q 1. What types of ions are formed:
(a) When an acid is dissolved in water.
(b) When a base is dissolved in water?

When an acid is dissolved in water, it forms hydrogen or H+ ions whereas when a base is dissolved in water, it forms hydroxide or OH- ions.


Q 2. Name the acid along with its chemical formula present in ant sting.

The acid present in ant sting is methanoic acid (formic acid). The chemical formula is HCOOH.

Explanation: When an ant stings, it leaves formic acid (Methanoic acid) which causes pain and irritation. To get relief from the sting, a mild base like baking soda on the stung area gives relief.

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FAQs on Overview: Acids & Bases - 1 - General Awareness & Knowledge - Bank Exams

1. What are acids?
Acids are chemical substances that release hydrogen ions (H+) when dissolved in water. They are typically sour-tasting and can also corrode metals and burn human skin. Some common examples of acids include lemon juice, vinegar, and hydrochloric acid.
2. How do acids and bases differ?
Acids and bases differ in terms of their properties and behavior. Acids release hydrogen ions (H+) when dissolved in water, while bases release hydroxide ions (OH-). Acids typically have a sour taste and can corrode metals, while bases have a bitter taste and can feel slippery. They also have different pH levels, with acids having a pH less than 7 and bases having a pH greater than 7.
3. What are bases?
Bases are chemical substances that release hydroxide ions (OH-) when dissolved in water. They are typically bitter-tasting and can feel slippery to the touch. Some common examples of bases include baking soda, soap, and ammonia.
4. How do bases and alkalis relate to each other?
Bases and alkalis are related because all alkalis are bases, but not all bases are alkalis. Alkalis are a specific type of base that can dissolve in water and release hydroxide ions (OH-). Therefore, while all alkalis are bases, not all bases are considered alkalis.
5. What is the difference between bases and alkalis?
The main difference between bases and alkalis lies in their solubility in water. Bases do not necessarily dissolve in water, while alkalis are bases that can readily dissolve in water. Alkalis are also commonly referred to as "water-soluble bases." Therefore, alkalis are a subset of bases that exhibit the ability to dissolve in water and release hydroxide ions.
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