Silicic acid is considerably weaker than carbonic acid. The KA for silicic acid is considerably smaller than for carbonic acid.At pH greater than 10, silica is present as silicate ions, and is quite soluble.At neutral pH, the ionization of silicic acid depends on the concentration of hydrogen ions. Since K1 for silicic acid is very small, not much silicic acid can ionize when H+ is present.