Question

Most metal oxides are insoluble in water but some of these dissolve in water. What are these oxides and their solutions in water called

Answer 1

Oxides of Metals like Sodium (Na2O), Potassium(K2O), Calcium(CaO), Magnesium(MgO) are soluble in water.
These oxides as well as metals are basic in nature, forming basic Oxides.
These oxides dissolve to form Bases, like:
2Na2O + 2H2O -----> 4NaOH
These bases are water soluble and are often referred to as 'Alkalies'.