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Ionic Equilibrium Formula For NEET Exam 2025

Ionic equilibrium formula addresses the balance of ions in a solution, crucial for understanding weak acids and bases, understand it and cover the NEET 2025 syllabus comprehensively.
authorImagePraveen Kushwah11 Mar, 2025
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Ionic Equilibrium Formula

Ionic Equilibrium Formula : Ionic equilibrium addresses the balance of ions in a solution, crucial for understanding weak acids and bases. The ionization constants (Ka for acids and Kb for bases) quantify ionization extents. Ka reflects the ionization of a weak acid HA, while Kb relates to a weak base B ionizing in water.

NEET Aspirants must go through it and practice the relevant questions to this. this way can comprehensively cover the NEET 2025 syllabus .

Ionic Equilibrium Formula

Ionic Equilibrium Formula has parameters, which predict pH or pOH. The Henderson-Hasselbalch equation connects pH, Ka, and the ratio of conjugate base to weak acid concentrations in buffers. Getting ionic equilibrium is essential for explaining substance behavior in solutions without forming strong chemical bonds.

Ostwald Dilution Law

The Ostwald Dilution Law describes the relationship between the degree of dissociation (α) of a weak electrolyte and its concentration when diluted. For a weak electrolyte AB dissociating into ions A^z+ and B^w-, the law is given by:

α = sqrt(Kc / C)

Where:
  • α is the degree of dissociation.
  • K_c is the equilibrium constant for the dissociation.
  • C is the initial concentration of the weak electrolyte.
This equation shows that as the solution is diluted (C decreases), the degree of dissociation tends to increase. The Ostwald Dilution Law is particularly applicable to weak acids and bases, providing insights into their behavior under different dilution conditions.

Ionization Constant (Ka for acids, Kb for bases)

The ionization constant, denoted as Ka for acids or Kb for bases, measures how much a weak acid or base ionizes in a solution. It's crucial in studying ionic equilibrium in aqueous solutions.
  1. Acid Ionization Constant (Ka): For a weak acid (HA) dissociating in water: HA ⇌ H⁺ + A⁻ The acid ionization constant is given by: Ka = [H⁺][A⁻] / [HA]
  2. Base Ionization Constant (Kb): For a weak base (B) reacting with water: B + H₂O ⇌ BH⁺ + OH⁻ The base ionization constant is given by: Kb = [OH⁻][BH⁺] / [B]
Both Ka and Kb values indicate the equilibrium position. Higher values suggest stronger acids or bases, meaning more extensive ionization. These constants are essential for understanding acid and base strengths, helping chemists predict their behavior in solutions.

pH Calculation

pH is a measure of the acidity or alkalinity of a solution and is defined as the negative logarithm (base 10) of the concentration of hydrogen ions ( ) in the solution. The pH scale ranges from 0 to 14, where lower pH values indicate acidic solutions, higher pH values indicate basic (alkaline) solutions and a pH of 7 represents a neutral solution. The pH of a solution is calculated using the formula:

pH = -log[H+]

pOH Calculation

The pOH is a measure of the hydroxide ion ( ) concentration in a solution and is the negative logarithm (base 10) of that concentration. It provides information about the basicity or alkalinity of a solution, analogous to how pH indicates acidity. Like pH, pOH is measured on a scale from 0 to 14, with lower values indicating more basic solutions and higher values indicating more acidic or neutral solutions. The pOH of a solution is calculated using the formula:

pOH = -log[OH-]

Relation between pH and pOH in Water

This relationship highlights that the sum of the pH and pOH in a solution, at any given moment, is always equal to 14. As pH increases, pOH decreases, and vice versa, reflecting the inverse relationship between the concentrations of hydrogen ions and hydroxide ions in water. A neutral solution (pure water) has a pH of 7 and a pOH of 7, making the sum equal to 14.

pH + pOH = 14

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical expression that relates the pH of a solution to the pKa (acid dissociation constant) and the ratio of the concentrations of the dissociated (ionized) and undissociated (unionized) forms of a weak acid or weak base. This equation is particularly useful in understanding and calculating the pH of buffer solutions. For an acid (HA) and its conjugate base (A⁻), the Henderson-Hasselbalch equation is given by:

pH = pKa + log([A-]/[HA])

For a base (B) and its conjugate acid (BH⁺), the equation is modified as follows:

pOH = pKb + log([BH+]/[B])

These formulas are fundamental for understanding the behavior of weak acids and bases in solution, calculating the pH and pOH of a solution, and applying the Henderson-Hasselbalch equation to buffer systems. Ka and Kb values are specific to each acid or base, indicating the degree of ionization or dissociation. The pH and pOH calculations help quantify the acidity or basicity of a solution.

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Ionic Equilibrium Formula FAQs

How to Calculate Ionic Equilibrium?

Ionic equilibrium is often calculated using the concept of equilibrium constants, such as Kc or Kp for chemical reactions. For acids and bases, the acid dissociation constant (Ka) or the base dissociation constant (Kb) is commonly used. These constants express the ratio of concentrations of products to reactants at equilibrium.

What is ionic equilibrium Class 11 example?

An example from Class 11 chemistry involves the ionization of a weak acid, like acetic acid (CH3COOH), in water: CH3COOH ⇌ CH3COO- + H+ This equation represents the dynamic equilibrium between the undissociated acid and its dissociated ions in a solution.

What is Ka in ionic equilibrium formula?

Ka is the acid dissociation constant, a measure of the strength of an acid in a solution. It is defined as the ratio of the concentrations of the dissociated ions (products) to the undissociated acid (reactant) at equilibrium. The Ka expression for acetic acid (CH3COOH) is given by: Ka = [CH3COO-][H+]/[CH3COOH]

What is the formula of equilibrium?

The general formula for an equilibrium reaction, representing the dynamic balance between reactants and products, is given by: aA + bB ⇌ cC + dD Here, A and B are reactants, C and D are products, and 'a', 'b', 'c', and 'd' are the stoichiometric coefficients. The equilibrium constant (K) expression for this reaction is given by: K = [C]c[D]d/[A]a[B]b
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