Water Dissociation: H+ & OH- Ions Upon Ionic Compound Addition

[Kyoma]

Pure water is made up of water molecules, no free moving ions. However, if you add an ionic compound, say copper sulfate into water, Cu²⁺ and SO₄^2- will be produced, so will H⁺ and OH^- ions.

Why will water molecules dissociate into hydrogen and hydroxide ions when an ionic compound is added? Why will the ionic compounds dissociate in water?

 

[Borek]

Pure water is made up of water molecules, no free moving ions. However, if you add an ionic compound, say copper sulfate into water, Cu²⁺ and SO₄^2- will be produced, so will H⁺ and OH^- ions.

That's incorrect, see water autodissociation.

 

[Kyoma]

Then why will some ionic compounds (or covalent compounds) dissociate only in the presence of water? What makes water so special?

 

[Borek]

High dipole moment and high dielectric constant, ions are solvated which to some extent neutralizes their charges and makes separation easier.

 

[sohel2012]

Hi,

As we know that in the electrolysis of water we get oxygen and hydrogen, but how, water dissosites as H+ and HO- , so H+ would go to the cathode and become H2(gas) but what would become of the OH- ion? how it will become O2?.