Important Chemistry Formulas For IIT JEE

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It is compulsory to qualify in the IIT JEE examination for getting admission to the undergraduate B. Tech, B.E. or B. Arch programs at top engineering colleges of India. There is a tough competition in the IIT JEE examination, as there are more than 16.84 lakhs students appearing in this exam and there are around 1.63 lakhs seats including all UG courses like civil, mechanical, electrical, etc. Every candidate gives their best to get through the IIT JEE examination and you need a unique studying strategy to secure good ranks in the examination. 

Chemistry is one of the most promising and scoring subjects in the syllabus of IIT JEE. During the last days of preparation, you need to have a quick revision of all important formulas of chemistry. So below are the important formulas of chemistry given topic-wise.

Important Formulas of Chemistry are Given below Topic-Wise

1. Formulas for Chemical Equilibrium

A. Law of mass action or chemical equilibrium

At equilibrium Condition,

rf = rb, i.e., 

rate of forward reaction = rate of backward reaction

Keq or Kc = (C)x (D)y / (A)a (B)b

Where, Kc = kf / kb

Where the braces and powers are used to indicate “molar concentration”.

B. Formula for Equilibrium Constant in terms of Partial Pressure

Kp = (Pcm1)(Pdm2) /( pan1)(pbn2)

Where Kp is equilibrium constant in terms of partial pressure.

C. Formula for Equilibrium Constant in terms of Mole Fraction

Kx = XcC XdD / XaA XbB

Where Kx is the equilibrium constant in terms of mole fraction.

D. Expression for Relation between Kp and Kc

Kp = Kc (RT)Δn

where R is gas constant 0.0821 liters.atm/degree/mole and Δn is the total number of molecules of the product – the total number of molecules of the reactants.

E. Relation between Equilibrium Constant and Standard Free Energy

ΔGo = – RT ln Keq


ΔGo = – 2.303RT log Keq

F. Formula for Reaction Quotient (Q)

The reaction quotient has the same algebraic formula as Keq but the current concentrations instead of specifically the equilibrium concentrations are used in calculations.

The expression for Q is

Q = (C)c (D)d/ (A)a (B)b

G. Formula for Degree of Dissociation

Degree of dissociation (ɑ) = No. of molecules dissociated/Total no.of molecules taken.

Dissociation constant, K(diss):

Kdiss = (alpha)2 . C/ (1-  alpha) mol dm-3

2. Formula for Ionic Equilibrium

A. Formula for Ostwald Dilution Law

Ostwald pointed out that the law of chemical equilibrium is applicable to ionic equilibrium.

K = (A)+ (B)- / (AB) = Ca.Ca / C (1-a)

Here a denotes alpha sign.

B. Formula for Representing Buffer Capacity 

Buffer Capacity = Number of moles of acid/ Base added to UL of solution/change in pH 

C. Formula for Solubility

Solubility is the weight of solute in grams present in 100ml of solvent. It is denoted by s and is expressed in mole per litre or gram per litre.

Solubility (s) = 1 / Concentration of common ions or number of common ions

D. Formula for Solubility Product

The solubility product constant Ksp is the equilibrium constant for the equilibrium established between a slightly soluble ionic compound and its ions in a saturated aqueous solution.

Ksp = (Xs)x. (Ys)y = Xx.Yy.(S)x+y

3. Formulas on Electrochemistry

A. Formula for EMF of cell

E0Cell = (standard reduction potential of cathode) - (standard reduction potential of anode) 

E0 Cell = E0 Cathode - E0 Anode = E0 Right - E0 Left

B. Formula for Nernst Equation

Dependence of electrode potential and EMF on concentration and temperature.

For electrode potential:

Mn+ + ne- ------- M(s)

E = E0 RT In M(s) / nF (Mn+)aq

C. Formula for Gibbs Free Energy Change

Gibbs free energy change in an electrochemical reaction can be expressed as the equivalent of the potential difference.

- Del G = nEF

D. Formula for Concentration Cell

E cell = -( 0.0592/2) log (a2/ a1)

E0 cell = 0

4. Formula on Solutions and Colligative Property

A. Formula for Concentration of a Solution

Concentration = Quantity of Solute / Volume of Solution 

B. Formula For Relative Lowering of Vapour Pressure

It is the ratio of lowering of vapour pressure to the vapour pressure of pure solvent.

Relative lowering of vapour pressure is given by,

= PA0 -p / pa0

C. Formula for Raoult’s Law

The vapour pressure of a solution is equal to the product of a mole fraction of the solvent and its vapour pressure in the pure state.

P / pA = (1-XB)

Where xA+xB = 1, therefore xA= 1-xB

D. Formula For Elevation of Boiling Point

Boiling point elevation = Tb - Tb0

Tb = Kb M.m /1000

E. Formula for Freezing Point Depression

Freezing point depression = Tf0 - Tf