Chemistry · Physical Chemistry

Redox Reactions formulas for JEE

Every Redox Reactions formula you need for JEE, grouped by concept.

FormulasRevision notes
11 formulas2 concepts
01Redox Reactions and Oxidation Number02Balancing Redox Reactions
01

Redox Reactions and Oxidation Number

7 formulas

Oxidation Number Sum Rule

∑i(O.N.)i×ni=z\sum_{i} (O.N.)_i \times n_i = z

The algebraic sum of the oxidation numbers of all atoms in a molecule or polyatomic ion must equal the net charge on the species.

applies whenApplicable to all neutral molecules and polyatomic ions.
oxidation-numbersum-rule

Standard Cell Potential

Ecell∘=Ecathode∘−Eanode∘E^{\circ}_{cell} = E^{\circ}_{cathode} - E^{\circ}_{anode}

Calculated by taking the difference between the standard reduction potential of the cathode and the anode.

applies whenStandard states (298 K, 1 atm, 1 M concentration).
electrochemistrycell-potentialjee-advanced

Combination Redox Reaction

A+B→CA + B \rightarrow C

General formula for a combination redox reaction where two components form a single product.

applies whenAt least one reactant (A or B) must be in its elemental form.
reaction-typescombination

Displacement Redox Reaction

X+YZ→XZ+YX + YZ \rightarrow XZ + Y

General equation for a displacement reaction where an element replaces another in a compound.

applies whenX must be more reactive (stronger reducing/oxidizing agent) than Y.
reaction-typesdisplacement

Gibbs Free Energy and Cell Potential

ΔG∘=−nFEcell∘\Delta G^{\circ} = -n F E^{\circ}_{cell}

Relationship between standard Gibbs free energy change and standard cell potential.

applies whenStandard states.
thermodynamicsgibbs-energyjee-advanced

Halogen Displacement

X2+2Y−→2X−+Y2X_2 + 2Y^{-} \rightarrow 2X^{-} + Y_2

General representation of a halogen displacement reaction in aqueous solution.

applies whenX must be positioned above Y in Group 17 (e.g., Cl displaces Br and I). Fluorine is an exception in water.
reaction-typeshalogensdisplacement

Nernst Equation

E=E∘−RTnFln⁡QE = E^{\circ} - \frac{RT}{nF} \ln Q

Relates the actual cell potential to the standard potential and the reaction quotient.

applies whenNon-standard conditions.
electrochemistrynernstjee-advanced
02

Balancing Redox Reactions

4 formulas

Equivalent Weight in Redox

E=Mn-factorE = \frac{M}{n\text{-factor}}

Equivalent weight is the molar mass divided by the total transferred electrons (n-factor).

applies whenGeneral redox stoichiometry.
equivalent-weighttitrationjee-advanced

n-factor for Redox Agents

n-factor=∣ΔO.N.∣×number of atoms per moleculen\text{-factor} = |\Delta O.N.| \times \text{number of atoms per molecule}

The n-factor (valency factor) for an oxidizing or reducing agent is the total change in oxidation state per molecule.

applies whenStandard redox reactions excluding disproportionation.
stoichiometryn-factorjee-advanced

n-factor for Disproportionation

nfactor=nox×nrednox+nredn_{factor} = \frac{n_{ox} \times n_{red}}{n_{ox} + n_{red}}

Calculates the overall n-factor when a single substance simultaneously acts as both an oxidizing and reducing agent.

applies whenDisproportionation reactions only.
n-factordisproportionationjee-advanced

Law of Chemical Equivalence

N1V1=N2V2  ⟹  (n1×M1)V1=(n2×M2)V2N_1 V_1 = N_2 V_2 \implies (n_1 \times M_1) V_1 = (n_2 \times M_2) V_2

In a redox titration, the number of equivalents of the oxidizing agent equals the equivalents of the reducing agent.

applies whenAt the equivalence point of a titration.
titrationstoichiometryjee-advanced
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