What is meaning of degree of dissociation in chemistry
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} = x^{2}
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.