Anjali Mishra Content Writer-SME
Content Writer-SME
Key Highlights
- The splitting of neutral molecules into positive and negatively charged ions is called ionization.
- The ionization of acids and bases is explained by the Arrhenius theory.
- Anions (Negatively charged ions) and cations (Positively charged ions) are formed in the process of ionization.
- H2SO4 and HCl are examples of strong acids whereas CH3COOH and HCOOH are weak acids.
- Strong bases such as KOH are considered good proton acceptors whereas strong acids can donate protons easily.
Ionization is a process of splitting neutral molecules into charged ions in a solution. The overall reaction occurs in the presence of catalysts such as water, heat, etc.
- Hydrogen and hydroxide ions are produced by the ionization of acids and bases.
- Acids and bases are categorized as strong and weak based on their degree of ionization.
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Key Terms: Ionization of acids and bases, Degree of ionization, Acids, Bases, Strong Acid, Strong Base
Ionization of Acids and Bases
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The degree of ionization is the ratio of the number of molecules participating in ionization to the total number of molecules.
- The equation for the degree of ionization is given as
∝ = Number of molecules participating in dissociation / Total number of molecules
(Here ∝ represents the degree of ionization)
- The value differs greatly in different acids and bases.
- Moreover, the strength of acids and bases is also determined by the degree of ionization.
Ionization of Acids and Bases in a Neutralization Reaction
Ionization of Acids
The equation for the ionization of acid (HCl) is given as:-
HCl (Aq.) → H+ + Cl-
- The strength of acid is measured by the Ka value which is expressed in the above equation as:
Ka = [H+ ] [Cl-] / HCl
Here, Ka is an equilibrium constant for acid which depends on the temperature and strength of acids).
Ionization of Bases
The equation for the ionization of base (NaOH) is given as:-
NaOH (Aq. ) → Na++ OH-
- The strength of acid is measured by the Kb value which is expressed in the above equation as:
Kb = [Na+ ] [OH-] / NaOH
Here, Kb is an equilibrium constant for acid which depends on the temperature and strength of bases).
Arrhenius's Concept of Acid and Base Ionization
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In chemistry, the concept of ionization of acids and bases is explained by utilizing the “Arrhenius Theory”. According to the theory proposed by him:
- The substances that give hydrogen or hydronium ions (H3O+ or H+) in an aqueous medium are called acids.
- Bases are substances that give hydroxide (OH–) ions on the dissociation in an aqueous solution.
Explanation of Arrhenius Acids and Bases Ionization
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Arrhenius states that acid-base dissociation equilibrium is a dynamic process. To clarify, he demonstrated using an acid HA that HA had a higher tendency to give electrons than H3O+. He deduced from above that HA functions as a strong acid in this situation. The equation is as :
HA + H2O ⇌ H3O+ + A+
Examples of Acids and Bases Ionization
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The complete ionization of acids and bases is represented as:
- CH3COOH + H20 ⇌ CH3COO- + H+ (Ionization of acetic acid in aqueous solution)
- NH4OH + H20 ⇌ NH4+ + OH-(Ionization of Ammonium Hydroxide in aqueous solution)
Sample Questions
Ques. What do you understand about the equilibrium constant (Ka)? (2 marks)
Ans. The equilibrium constant (Ka) is the constant used for the ionization of acid. It depends only on temperature. This can be calculated in the equation HA + H2O ⇌ H+ + A_ as:
Ka = [H+ ] [A_ ] / [HA]
Ques. What are strong acids? (2 marks)
Ans. A strong acid is a type of acid that is completely ionized in an aqueous solution. For example- Hydrochloric acid (HCl) is a strong acid because it is dissociated completely into H+ and Cl- ions.
Ques. What are the factors that affect the ionization of acids? (2 marks)
Ans. The ionization of acids is affected by two important factors:
- Strength of bonds
- Stability of ions
Ques. What is the formula for calculating ionization percentage? (2 marks)
Ans. The ionization percent can be calculated as the ratio of the number of ions to the initial number of molecules and multiplied by 100. Mathematically, the equation can be given as–
Ionization % = (No. Of ions / Initial No. Of molecules) * 100
Ques. What is the pH value? (2 marks)
Ans. In chemistry, pH means the potential of hydrogen. The nature of acid depends on the pH value. It can be represented as
pH = -log[H+]
Here [H+] is the molar concentration of hydrogen ions.
Ques. What does it signify if the degree of ionization is 1? (2 marks)
Ans. The strength of acids or bases determines the degree of ionization. If the value of the degree of ionization of any compound is 1, it signifies the complete ionization of that compound in an aqueous solution.
Ques. What is a neutralization reaction? (2 marks)
Ans. The reaction in which acid and base of equal strengths react together to give salt and water is called a neutralization reaction. The general equation of a neutralization reaction can be given as
HCl (Acid) + NaOH (Base) —-> NaCl (Salt) + H2O (Water)
Ques. What are the examples of strong acids and weak acids? (3 marks)
Ans. When acids are completely ionized in an aqueous solution, they are called strong acids. On the other hand, weak acids are partially ionized.
- The most common examples of strong acids are Hydrochloric (HCl), and Sulphuric acid (H2SO4).
- Acetic acid (CH3COOH) and Formic acid (HCOOH) are the two examples of weak acids.
Ques. What are the examples of strong bases and weak bases? (3 marks)
Ans. When bases are completely ionized in an aqueous solution and give hydroxide (OH-) ions in a large quantity, they are called strong bases. The partial ionization of base gives a small amount of OH- ions and is called weak bases.
- Potassium hydroxide (KOH) and Sodium hydroxide (NaOH) are the two most commonly used strong bases in chemistry.
- Examples of weak bases are Ammonia, Aluminium Hydroxide, Lead Hydroxide, etc.
Ques. How does water play a role in the ionization of acids and bases? (3 marks)
Ans. Water plays a very significant role in the ionization of acids and bases. Water can react with both acids and bases.
- Water accepts the hydrogen ions when it is mixed with acid. Thus, it acts as a base in this case.
- The mixing of water with the base gives hydroxide ions. Thus, by donating hydrogen ions in this case, water acts as acid.
Ques. What are the uses of acids, bases, and salt in daily life? (2 marks)
Ans. Acids, bases, and salts have various roles in our daily lives such as
- In the production of fertilizers,
- Used as disinfectants,
- Making soaps and detergents, etc.
Ques. What is a conjugate acid-base pair?
A conjugate acid-base pair is a pair of molecules that can take up and donate hydrogen ions to each other.
Ques. Does ionization make the pH higher or lower? (2 marks)
Ans. Higher alkalinity is indicated by a higher concentration of hydronium ions, while lower concentrations are associated with higher pH, which indicates higher acidity.
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