Silica is insoluble in

1) SiO2+6HF→H2SiF6 Fluosilisicacid +2H2OSiO2 is soluble in HF due to the formation of fluorosilicic acid and hence HF is used for ETCHING process 2) SiO2+2NaOH→Na2SiO3+H2O Acid  (aq)  (Base)  sodiumsilicate  (Waterglass)  3) SiO2 Acid +2KOH( Base )(aq)→K2SiO3+H2OSiO2 is soluble in base like NaOH , KOH due to the formation of soluble silicatesSiO2 donot soluble in any other solventsSiO2 is only soluble in HF(acid) and insoluble in other acids