About half of the sodium carbonate produced is used in making glass products because it lowers the melting point of sand, the major component of...

About half of the sodium carbonate produced is used in making glass products because it lowers the melting point of sand, the major component of glass. When sodium carbonate is added to water it hydrolyses according to the following reactions.

CO32-(aq) + H2O(l) HCO3-(aq) + OH-(aq) K1

HCO3-(aq) + H2O(l) H2CO3(aq) + OH-(aq) K2

These can be combined to yield

CO32-(aq) + 2H2O(l) H2CO3(aq) + 2OH-(aq) K3

What is the value of K3? and Explain?