Ionic Equilibrium Formula For NEET Exam 2026
Ionic Equilibrium is an important NEET Chemistry chapter covering ionization of acids and bases, pH, buffer solutions, and solubility equilibria. With the NEET exam cancelled and the re-exam scheduled for the 21st June 2026, students can use this time for focused revision. Admit cards are expected to be released soon, making this chapter essential for last-minute preparation and formula revision.
Praveen Kushwah13 Jun, 2026
Ionic Equilibrium is an important chapter in NEET Chemistry that explains the balance of ions in solutions and the behaviour of acids, bases, and salts. It covers key concepts such as ionization of weak acids and bases, ionization constants (Ka and Kb), pH, buffer solutions, and solubility equilibrium. With the NEET exam cancelled and the re-exam scheduled for the 21st June 2026, this chapter becomes important for focused revision. Aspirants should revise all formulas and practice relevant questions from Ionic Equilibrium to strengthen their preparation before the re-exam. Admit cards are expected to be released soon.
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.
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.- 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]
- 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]
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.Prepare for NEET with PW Online NEET Coaching! Our courses offer structured lessons, clear explanations of concepts, and interactive classes to support your NEET preparation effectively.
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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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