Question

Which of these is the correct equation for the dissociation of water? H2O + H2O+<==> H2O + OH– H2O + H2O <==> H3O+ + OH– H2O <==> H+ + OH– H+<==> H2O + H2O+ H2O + OH–<==> H2O+

Answer 1

Answer:

Option b = H2O + H2O <==> H3O+ + OH–

Explanation:

Dissociation of water:

The water molecule dissociate into the hydroxyl ion and hydrogen ion. The hydrogen ion immediately protonate the other water molecule and form the hydronium ion.

Chemical equation:

H2O + H2O <==> H3O+ + OH–

The equilibrium constant of self ionization of water is given below:

Kw= [H3O+][OH-]

[H3O+] is the concentration of hydronium ion while [OH-] is the concentration of hydroxyl ion.

Kw is called ionic product of water. The value of Kw is 1.0 × 10∧-14  at 25 °C.

The pure water consist of equal concentration of hydroxyl and hydrogen ions. In order to determine the molarity of both ions square root of ionic product (Kw) is taken.

   [OH-]=[H+]= 1.0 × 10∧-7 M

In case of acidic solution concentration f hydrogen ions are greater than hydroxide ions. For example,

HCl when dissociate into water gives H+ and Cl-. The H+ ions increases in solution. The equilibrium is this given by water.

H2O ⇆ H+ + OH-

Reaction is forced to wards left. As a result concentration of hydroxide ions decreases.

In case of base solution like KOH when dissociate it gives K+ and OH -. The concentration of hydroxyl ions increases in this case and concentration of H+ is decreases and ionic product remain constant.