CUET Chemistry 2026 Reactions & Formulas – Quick Revision Guide

With the CUET 2026 exam starting from 11 May, this is the most important time for quick revision of Chemistry formulas and important reactions. In the last few days before the exam, students should focus more on high-weightage concepts, numerical formulas, and frequently asked Inorganic Chemistry reactions instead of studying new topics.

Here will help you revise all the important Physical Chemistry formulas and key Inorganic Chemistry reactions in one place. Topics like Electrochemistry, Solutions, Chemical Kinetics, Dichromate, and Permanganate reactions are commonly asked in CUET 2026, so revising them properly can improve accuracy, save time in the exam, and help boost your overall Chemistry score.

CUET Chemistry 2026 Reactions & Formulas 

These are the most important Chemistry formulas for CUET preparation, covering Solutions, Electrochemistry, and Chemical Kinetics for quick revision and numerical practice. 

Chapter 1: Solutions

Concentration Terms

• Weight by Weight Percentage: (Weight of component / Total weight) × 100

• Volume by Volume Percentage: (Volume of component / Total volume) × 100

• Weight by Volume Percentage: (Weight of component / Total volume) × 100

• Note: These percentages are unitless, requiring only the percentage symbol.

• Parts Per Million (PPM):

• Use Cases: Used for extremely small solute amounts, such as pollutants in air or minerals in water.

• Formula: (Weight of solute / Total weight) × 10⁶

• Unit: ppm

• Molarity (M):

• Definition: Moles of solute per liter of solution.

• Formula: (Moles of solute / Volume of solution in Liters)

• Unit: Mole/Liter (or M)

• Molality (m):

• Definition: Moles of solute per kilogram of solvent.

• Formula: (Moles of solute / Weight of solvent in kg)

• Unit: Mole/kg (or m)

• Mole Fraction (χ):

• Definition: Moles of one component divided by the total moles of all components.

• Formula: (Moles of component A / Total moles of all components)

• Properties: Sum of mole fractions is always one. It is unitless.

• Density of Solution: Total weight / Total volume.

Solubility: Henry's Law

This law describes the solubility of a gas in a liquid, such as dissolving CO₂ in soft drinks. The partial pressure of the gas above the liquid is directly proportional to its mole fraction (solubility) in the liquid phase.

• Formula: P = KH χ (where KH is Henry's Law constant).

• Interpretation of KH: If KH is high, the gas is less soluble; if KH is low, the gas is highly soluble.

Raoult's Law

This law applies to liquid-liquid solutions with volatile components. The partial vapor pressure of each component in a solution is directly proportional to its mole fraction in the solution.

• Formula:

• PA = P°A χA

• PB = P°B χB

• Total Pressure (P_total) = PA + PB

• Mole Fraction in Vapor Phase (yA, yB): yA = PA / P_total

Comparison: Henry's Law vs. Raoult's Law

Colligative Properties

These are properties of dilute solutions that depend only on the number of solute particles, not their nature. They apply when a non-volatile solute is added to a pure solvent in dilute amounts.

1. Relative Lowering of Vapor Pressure (RLVP):

• Formula: (P° - P_solution) / P° = χ_solute

2. Elevation in Boiling Point (ΔTb):

• Formula: ΔTb = Kb × m (Kb is molal elevation constant, m is molality).

• Calculation: ΔTb = T_solution - T°_solvent

3. Depression in Freezing Point (ΔTf):

• Formula: ΔTf = Kf × m (Kf is molal depression constant, m is molality).

• Calculation: ΔTf = T°_solvent - T_solution

4. Osmotic Pressure (π):

• Formula: π = CRT (C is Molarity, R is gas constant, T is temperature in Kelvin).

Van't Hoff Factor (i)

This factor is very important for CUET and accounts for changes in the number of solute particles due to association or dissociation in solution, impacting colligative properties.

• Effect on Formulas: Colligative properties are multiplied by i:

• (P° - P_solution) / P° = i χ_solute

• ΔTb = i Kb m

• ΔTf = i Kf m

• π = i CRT

• Basic Formula: i = (Number of particles after dissociation/association) / (Number of particles before dissociation/association)

• Interpretation:

• Association: Particles join, i < 1.

• Dissociation: Particles break apart, i > 1.

• Determining 'i':

1. Non-electrolytes (e.g., glucose, urea): i = 1.

2. Strong Electrolytes (strong acids/bases, salts): i = number of ions produced (e.g., KCl: i=2; K₂SO₄: i=3).

3. Weak Electrolytes (weak acids/bases):

• For Association: i = 1 + α (1/n - 1)

• For Dissociation: i = 1 + α (n - 1) (where α is degree of dissociation/association, n is number of particles).

Chapter 2: Electrochemistry

• Standard Cell Potential (E°cell): E°cell = E°cathode - E°anode

• Nernst Equation: Calculates cell potential (Ecell) under non-standard conditions.

• General Formula: Ecell = E°cell - (RT/nF) ln Q

• Memory Tip: At 298 K (25°C), the Nernst equation simplifies to Ecell = E°cell - (0.059/n) log Q for quick calculations.

• At equilibrium, Ecell = 0, allowing calculation of the Equilibrium Constant (K_eq).

• Conductivity (κ):

• Formula: κ = G × (l/A) (G is conductance, l/A is cell constant).

• Unit: Siemens meter⁻¹ (S m⁻¹)

• Molar Conductance (Λm):

• Formula: Λm = (κ × 1000) / M (κ is conductivity, M is Molarity).

• Unit: Siemens meter² mol⁻¹ (S m² mol⁻¹)

• Molar Conductance vs. Concentration:

• Strong Electrolytes: Molar conductance decreases sharply with increasing concentration.

• Weak Electrolytes: Molar conductance increases sharply at very low concentrations.

• Degree of Dissociation (α): α = Λm / Λm°

• Dissociation Constant (Ka): Ka = Cα² / (1 - α)

• Kohlrausch's Law: The limiting molar conductivity of an electrolyte at infinite dilution is the sum of the limiting ionic conductivities of its individual cations and anions.

• Faraday's Laws of Electrolysis:

1. First Law: Mass (w) deposited at an electrode is proportional to the quantity of electricity (Q) passed.

• Formula: w = (E / 96500) × Q (E is equivalent weight).

• Equivalent Weight (E): E = Molar Mass / Charge.

2. Second Law: When the same quantity of electricity passes through different electrolytes, masses deposited are proportional to their equivalent weights.

• Formula: (w1 / w2) = (E1 / E2)

Chapter 3: Chemical Kinetics

• Rate of Reaction:

• Formula: Rate = Δ[Concentration] / ΔTime

• Sign Convention: Negative for reactants (concentration decreases), positive for products (concentration increases). Divide by stoichiometric coefficients.

• For aA + bB → cC + dD: Rate = -(1/a) Δ[A]/Δt = +(1/c) Δ[C]/Δt

• Rate Law: Rate = k [A]^n [B]^m … (k is rate constant, n, m are reaction orders).

• Integrated Rate Laws:

1. Zero-Order Reaction: [A]t = [A]₀ - kt

2. First-Order Reaction: ln([A]₀ / [A]t) = kt (or 2.303 log([A]₀ / [A]t) = kt)

• Half-life (t½): t½ = 0.693 / k. It is constant.

• Arrhenius Equation: Relates rate constant (k) to temperature (T) and activation energy (Ea).

• Formula: k = A e^(-Ea/RT) (A is Arrhenius factor).

• Temperature Dependence of Rate Constant:

• Formula: ln(k₂ / k₁) = (Ea / R) × (1/T₁ - 1/T₂)

• Effect of Catalyst: A catalyst provides an alternative reaction pathway with a lower activation energy (Ea), increasing the rate constant.

Important Reactions of Inorganic Chemistry

These are the most important Inorganic Chemistry reactions for CUET preparation, including Copper, Dichromate, and Permanganate reactions frequently asked in exams. 

Reactions of Copper

• Copper (Cu²⁺) with halides:

• With Cl⁻ and F⁻: Copper remains in the +2 oxidation state.

• With I⁻: This is a very important reaction. Cu²⁺ is reduced to Cu⁺, forming Cu₂I₂ precipitate and liberating I₂.

• 2Cu²⁺(aq) + 4I⁻(aq) → Cu₂I₂(s) + I₂(s)

• Disproportionation of Cu⁺: In aqueous medium, Cu⁺ is unstable and disproportionates (simultaneously oxidized and reduced).

• 2Cu⁺(aq) → Cu²⁺(aq) + Cu(s)

• Reason: Cu²⁺ is more stable in aqueous phase due to higher hydration energy.

Preparation of Potassium Dichromate (K₂Cr₂O₇)

Prepared from Chromite Ore (FeCr₂O₄):

1. Roasting: 4FeCr₂O₄ + 8Na₂CO₃ + 7O₂ → 8Na₂CrO₄ + 2Fe₂O₃ + 8CO₂

2. Conversion: 2Na₂CrO₄ + H₂SO₄ → Na₂Cr₂O₇ + Na₂SO₄ + H₂O

3. K₂Cr₂O₇ formation: Na₂Cr₂O₇ + 2KCl → K₂Cr₂O₇ + 2NaCl

Interconversion of Chromate (CrO₄²⁻) and Dichromate (Cr₂O₇²⁻)

This interconversion is very important for exams. Both contain chromium in the +6 oxidation state.

• Chromate (CrO₄²⁻): Yellow, stable in basic medium.

• Dichromate (Cr₂O₇²⁻): Orange, stable in acidic medium.

• Interconversion Reactions:

• Dichromate → Chromate (in Basic Medium): Cr₂O₇²⁻ (orange) + 2OH⁻ ⇌ 2CrO₄²⁻ (yellow) + H₂O

• Chromate → Dichromate (in Acidic Medium): 2CrO₄²⁻ (yellow) + 2H⁺ ⇌ Cr₂O₇²⁻ (orange) + H₂O

Oxidizing Nature of Chromium(VI) Compounds (Dichromate)

Chromium in the +6 oxidation state acts as a strong oxidizing agent, getting reduced from Cr(VI) to Cr(III), typically in acidic medium.

• Key Oxidations: I⁻ → I₂, Sn²⁺ → Sn⁴⁺, Fe²⁺ → Fe³⁺, H₂S → S.

Preparation of Potassium Permanganate (KMnO₄) and Potassium Manganate (K₂MnO₄)

Prepared from Pyrolusite Ore (MnO₂):

1. Manganate formation: 2MnO₂ + 4KOH + O₂ → 2K₂MnO₄ + 2H₂O

2. Permanganate formation (from Manganate): In acidic medium, K₂MnO₄ disproportionates.

• 3MnO₄²⁻ + 4H⁺ → 2MnO₄⁻ + MnO₂ + 2H₂O

3. Decomposition of Permanganate on Heating: 2KMnO₄ (s) → K₂MnO₄ (s) + MnO₂ (s) + O₂ (g)

Oxidizing Nature of Manganese(VII) Compounds (Permanganate)

Manganese in the +7 oxidation state (KMnO₄) is a strong oxidizing agent, getting reduced. The products vary with pH:

• In Acidic Medium (H⁺): Mn(VII) reduces to Mn²⁺.

• In Neutral or Weakly Basic Medium (OH⁻): Mn(VII) reduces to MnO₂ (Mn(IV)).

• Key Oxidations:

• In Acidic Medium: Fe²⁺ → Fe³⁺, I⁻ → I₂, H₂O₂ → O₂, SO₂ → H₂SO₄, NO₂⁻ → NO₃⁻, C₂O₄²⁻ → CO₂, H₂S → S.

• In Basic Medium: I⁻ → IO₃⁻ (distinct from acidic medium).

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