Soap is a sodium or potassium salt of a fatty acid, typically called sodium stearate (C₁₇H₃₅COONa) when made from stearic acid.

Water is amphoteric, meaning it can act as both an acid and a base depending on the substance it reacts with.

Na₂CO₃ behave like a base in water because it dissociates to form carbonate ions (CO₃²⁻), which accept protons (H⁺) and release hydroxide ions (OH⁻).

NaHCO₃ (sodium bicarbonate) is a weak base because it reacts with acids to release carbon dioxide (CO₂) and forms a weak basic solution.

A strong acid completely dissociates in water, while a concentrated acid refers to the amount of acid present in a solution, regardless of its dissociation.

Arrhenius Concept of Acid and Base:

1. Arrhenius Acid:

a) Definition:

An acid is that substance which dissociates in water to give proton (H⁺) or hydroxonium ion (H₃O⁺).

b) Example:

               H₂​O​

 HCl(aq)​    ⇌   H₃O⁺(aq)+​+Cl⁻(aq)

2. Arrhenius Base:

a) Definition:

A base is that substance which dissociates in water to give hydroxyl ions (OH⁻).

b) Example: 

                  H₂​O​

NaOH(aq)​   ⇌     Na⁺(aq) ​+ OH⁻(aq)

3. Role of Water in Arrhenius Concept:

i). Water has an essential role to play in Arrhenius concept of acids and bases.

ii). Whenever an acid or a base dissociate in water, its molecules participate in reaction by surrounding the resultant proton (H⁺) and hydroxl ion (OH⁻).

iii). Since proton is very small in size and its charge density is very high, it forms a strong bond with the lone pair of water molecules to give hydroxonium ion, H₃O⁺.

Arrhenius Concept:

i). Acid:

An acid is that substance which dissociates in water to give proton (H⁺) or hydroxonium ion (H₃O⁺).

Example:

HCl(aq)    ⇌    H₃O⁺(aq) + Cl⁻(aq)
              H₂O

ii). Base:

 A base is that substance which dissociates in water to give hydroxyl ions (OH⁻).

Example:

NaOH(aq)     ⇌     Na⁺(aq) + OH⁻(aq)
                    H₂O

Brønsted-Lowry Concept:

i). Acid:

An acid is a substance that donates a proton.

Example:

 HCl    + H₂O   ⇌   H₃O⁺(aq) + Cl⁻
(Acid)   (Base)

ii). Base:

A base is a substance that accepts a proton.

Example:

 HCl   + H₂O   ⇌   H₃O⁺(aq) + Cl⁻(aq)
(Acid)  (Base)

Arrhenius Concept:

i). Acid:

An acid is that substance which dissociates in water to give proton (H⁺) or hydroxonium ion (H₃O⁺).

Example:

HCl(aq)    ⇌    H₃O⁺(aq) + Cl⁻(aq)
              H₂O

ii). Base:

 A base is that substance which dissociates in water to give hydroxyl ions (OH⁻).

Example:

NaOH(aq)     ⇌     Na⁺(aq) + OH⁻(aq)
                    H₂O

Brønsted-Lowry Concept:

i). Acid:

An acid is a substance that donates a proton.

Example:

 HCl    + H₂O   ⇌   H₃O⁺(aq) + Cl⁻
(Acid)   (Base)

ii). Base:

A base is a substance that accepts a proton.

Example:

 HCl   + H₂O   ⇌   H₃O⁺(aq) + Cl⁻(aq)
(Acid)  (Base)

1). Reaction with Ammonium Chloride:

a) Reaction:

H₂SO₄ + NH₄Cl   --->  NH₄HSO₄ + HCl

b) Explanation:

Sulphuric acid reacts with ammonium chloride to form ammonium bisulphate (NH4HSO4) and release hydrogen chloride (HCl) gas.

2). Reaction with Ammonium Nitrate:

a) Reaction:

H₂SO₄ + NH₄NO₃  -- -> NH₄HSO₄ + HNO₃

b) Explanation:

Sulphuric acid reacts with ammonium nitrate to form ammonium bisulphate (NH₄HSO₄) and nitric acid (HNO₃). 

3).Reaction with Magnesium Oxide:

a) Reaction:

H₂SO₄+ MgO   --> MgSO₄+  H₂O

b) Explanation:

Sulphuric acid reacts with magnesium oxide to form magnesium sulphate (MgSO₄) and water (H₂O).

4). Reaction with Magnesium Carbonate:

a) Reaction:

H₂SO₄+ MgCO₃---> MgSO₄ + CO₂ +H₂O

b) Explanation:

Sulphuric acid reacts with magnesium carbonate to form magnesium sulphate (MgSO₄), carbon dioxide (CO₂) and water (H₂O).

When a base reacts with a non-metallic oxide, an acid is formed. This reaction can be represented as:

Base + Non-metallic oxide → Acid + Water

Reaction Example:

2NaOH(base) + CO₂(non-metallic oxide) → Na₂CO₃(acid) + H₂O

Nature of Non-Metallic Oxide:

From this reaction we can infer that:

• Non-metallic oxides are acidic in nature.
• They react with bases to form acids and water, which is a characteristic property of acids.

1. Dry HCl Gas:

Reaction:

 HCl   +  H₂O  ⇌  H₃O+(aq) + Cl⁻
(acid)    (Base)

Reason:

 In this reaction, HCl gas acts as an acid because it donates its proton to water which acts as a base.

2. HCl Solution in Water:

Reaction:

Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)

Reason:

HCl reacts with reactive metals like Mg. It forms salts and evolves hydrogen gas. 

Reaction:

CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)

Reason:

HCl decomposes metal carbonates and hydrogen carbonates, evolving carbon dioxide gas.

1. Acid:

a. Definition:

 An acid is a substance (molecule or ion) that can donate a proton (H⁺) to another substance.

b. Example:

HCl(aq) + NH₃(aq) ⇌ NH₄ +(aq) +Cl⁻(aq)

2.  Conjugate Base:

a. Definition:

 A conjugate base is a species formed when an acid donates a proton.

b. Example:

HCl(aq) + H₂O(aq) ⇌ H₃O⁺(aq) +Cl⁻(aq)

3. Explanation:

i) It is a reversible reaction.
ii) In the forward reaction HCl is an acid as it donates a proton, whereas H₂O is a base as it accepts a proton.
iii) In the reverse reaction Cl⁻ ion is a base as it accepts a proton from acid H₃O⁺ ion.
iv) Cl⁻ ion is called the conjugate base of acid HCl.

i). Acids are essential for various biochemical processes in the human body. For example, hydrochloric acid (HCl), in the stomach acids in digestion by breaking down food and killing harmful bacteria.

ii). Additionally, acids like amino acids are the building blocks of proteins and carbonic acid helps in regulating blood pH and maintaining the body's acid-base balance. 

1. For a Short Duration:

Lime water Ca(OH)₂ turns milky due to the formation of calcium carbonate CaCO₃.

a. Reaction:

CO₂ +  Ca(OH)₂   → CaCO₃ + H₂O
          Lime water

 2. For a Long Duration:

The milkiness disappears as calcium carbonate dissolves in excess CO₂ to form calcium bicarbonate Ca(HCO₃)₂.

a. Reaction:

CaCO₃      + CO₂   + H₂O    →Ca(HCO₃)₂
Calcium      Carbon     Water
Carbonate    Dioxide