What is meaning of degree of dissociation in chemistry

Question

What is meaning of degree of dissociation in chemistry

Answer 1

Let's take an example.  The degree of dissociation can be expressed as a percent.  Let's find the % dissociation of water.  We will use a liter of water since we know some basic data linked specifically to one liter of water. Of course it would be the same % for any amount of water at STP.

 

HOH  <======----> H⁺  +   OH ^-   with

 

K_diss = 1 x 10^-14   =    [H+]  [OH-] 

 

 

[H⁺]  =  [OH^-]  =  x, so

 

 

Kdiss = 1 x 10^-14 = x²

 

x = 1 x 10^-7

 

% dissociation = number of moles of HOH that dissociated in one liter of water divided by the original number of moles of HOH in one liter of water.

 

% dissociation = (1 x 10^-7 moles of water dissociated) divided by (56 moles of water to begin with)

 

% dissociation = 1.7857142857142857142857142857143e-7 %

 

You wonder where 56 came from.  It is the number of moles of water in a liter.  You see, this is all in moles per liter, so if you don't already know, I should show you how to find out there are 56 moles of water in a liter of water.

 

One mole of water has a mass of about 18 grams per mole.  One liter of water has a mass of about 1000 g.

Dividing we see that there are 1000/18 moles of water in a liter, or 55.6 moles of water per liter of water.

 

Answer 2

The Degree of dissociation in chemistry is a general process in which molecules (or ionic compounds such as salt or complexes) separate or split into smaller particles such as atoms, ions or radicals, usually in a reversible manner. For instance, when an acid dissolves in water, a covalent bond between an electronegative atom and a hydrogen atom is broken by heterolytic fission, which gives a proton (H+) and a negative ion. Dissociation is the opposite of association and recombination. If you need more information go to Wikipedia.com