Ionic Equilibrium Formulas for NEET

Ionic equilibrium states that in a chemical reaction when a given substance dissolves in water, it splits into ions. So, when the temperature, pressure, and concentration remain constant before and after the reaction, we say that the chemical reaction is in equilibrium. 

In case, the equilibrium establishes between the unionized molecules and the ions in the solution of weak electrolytes, it is an ionic equilibrium.

In this article, we will understand what is ionic equilibrium, ionic equilibrium formulas for NEET, the formula of ionic equilibrium,  chemical and ionic equilibrium formulas. Also, we will have a look at the formula sheet for ionic equilibrium.

What is Ionic Equilibrium in Chemistry?

Firstly, to understand what is ionic equilibrium, let’s have a look at the following  reversible reaction:

              CH3COOH    ⇔   CH3COO–    +    H– 

Here, we can see that acetic acid is a weak acid and it dissociates into two ions, viz: CH3COO–    +    H–.  

As a matter of fact, electrolytes are chemical substances, like CH3COOH conduct electricity. Since CH3COOH is a weak electrolyte, so there is low conductivity.  

The conduction of electricity takes place by the movement of ions. Also, acetic acid dissociates to a lesser extent in an aqueous solution, so we can say that the low conductivity is because of the less flow of ions.

Ionic Equilibrium Formulas for NEET

Under ionic equilibrium formulas, we have the following list of chemical and ionic equilibrium formulas:

• Degree of Dissociation

• Ostwald Dilution Formula

• pH Scale

• pOH Scale

• Properties of Water

• Ionic Product of Water

• Solubility Product

• Degree of Hydrolysis

Degree of Dissociation

is the degree of dissociation. It is the extent to which an electrolyte dissociates into ions in a given solution. It is given by the following formula:

             α  =      number of molecules ionized or dissociatedtotal number of molecules taken 

For a weak electrolyte,  α < 1.

For any strong electrolyte (that dissociates completely into its ions), say KCl:

                        KCl    ⇔    K+    +  Cl–      (α =  1)

So, we define the degree of dissociation of a weak electrolyte: it varies directly with the dilution that is alpha maximum at infinite dilution.

Ostwald Dilution Law

Now, let us apply Ostwald dilution law to the ionic equilibrium formula:

                           K   = [A+} {B-1][AB]  =   C . CC (1 -  )  

                          K   =   C2 (1 -  )

pH Scale

For finding the pH of a solution, we check the concentration of H+  ion, so the formula goes like this:

                     pH    =    - log10 [H+]

Or,

                     pH     =    log10 1[H+]

pOH Scale

Similarly, we use pOH for determining the concentration of OH–  ions in a solution, so we have:

                      [OH–] =  10-pOH

Or,

                   pOH  =  - log10 [OH–]

Or, 

                      pOH     =    log10 1[OH-]                

Also,          pH  +  pOH   =   1

And,            pH  +  pOH   =  pKw

Besides this, we have another formula for acidic solutions:

            pKa   =   - log10 pKa 

Also,

            pKa  1Ka 1Acidic Strength

Additionally, for basic solutions:

                   pKb   =   - log10 Kb 

It can be written as;

                    pKb   1Kb 1Basic Strength

Properties of Water

In pure water, the concentration of H+ equals the concentration OH- concentration. So, the molar concentration/molarity of water equals 55.56 M.

Here, molarity is the concentration of the substance. Mathematically, we calculate it by the following formula:

Molar concentration = no. of moles of solute that gets dissolved in per litre of solution 

In short,

                             M  =  n/V 

Also, M is measured in moles/litre.

Ionic Product of Water

In a given solution, the ionic product is the product of the molar concentration of H+, H3O+, or OH-  ions. We denote the ionic product of water by Kw.

So, 

               Kw = [H3O+].[OH-]

Also,

               Kw  = Ka. Kb 

And,

                pKw  = pKa  +  pKb

At room temperature, i.e., 25℃, the ionic product of water is:

             Kw  =   1 * 10 

So, 

               pKw  =  14

Here, we can see that the value of Kw increases with the temperature rise.

Buffer Solution

A buffer solution is a solution whose pH does not alter even on adding the strong acid or base to it. 

We also call the buffer solution as the reserve acidity or basicity of the solution because it resists change in pH value and this action to prevent the pH change is called buffer action or the buffer capacity.

We denote the buffer solution with a symbol or phi.A mathematical formula for the buffer capacity is as follows:

                                           =  No of moles of acid or base added to a litre of solutionchange in pH

Since both the values in the numerator and denominator are constant values, so the buffer capacity is unitless.

Solubility Product

We define solubility as the weight of solute in grams present in 100 g of solvent. The solubility is symbolized as ‘s’ and expressed in mole per litre or gram per litre.

The solubility product formula is:

                 s   =       1Concentration of common ions or number of common ions 

Or,

                   Ksp  =  (xs)x. (xy)y  =  xx. yy (s)(x + y)

Degree of Hydrolysis

The degree of hydrolysis or h = Number of moles of salt hydrolyzed per the total moles of the salt taken.

Conclusion

In any solution, the molecule and its dissociated ions remain in equilibrium. So, ionic equilibrium exists only in a weak electrolyte. Also, to resist any change in pH value, there’s a solution called the buffer solution.