The reactions of the oxides of the elements Na–S with water

• Reaction of sodium oxide with water:

  Equation: $Na_2O+$$H_2O\ \rightarrow\ 2NaOH$

  Equation showing ions formed: $Na_2O+$$H_2O\ \rightarrow\ 2Na^+$$+$$2OH^-$

  A mixture of sodium oxide and water has a pH of 12-14.
• Reaction of magnesium oxide with water:

  Magnesium oxide is sparingly soluble in water but some does react to form magnesium hydroxide. 

  Equation: $MgO+$$H_2O\ \rightarrow\ Mg\left(OH\right)_2$

  A mixture of magnesium oxide and water has a pH of 9.
• Reaction of aluminium oxide with water:

  Aluminium oxide does not dissolve in water or react with water due to the strength the ionic bonds between the oppositely charged, small ions.  Furthermore, a protective oxide layer prevents this reaction, therefore preventing corrosion.

  A mixture of aluminium oxide and water has a pH of 7.
• Reaction of silicon dioxide oxide with water:

  Silicon dioxide does not dissolve in or react with water as the water cannot supply enough energy to break the strong covalent bonds. The pH of the mixture of silicon dioxide and water is 7. 
• Reaction of phosphorus(V) oxide with water:

  Phosphorus (V) oxide reactions with water producing phosphorus (V) acid. 

  $P_4O_{10}+$$6H_2O\ \rightarrow\ 4H_3PO_4$
• Reaction of sulfur dioxide with water:

  Sulfur dioxide reacts with water producing sulfuric (IV) acid. 

  $SO_2+$$H_2O\ \rightarrow\ H_2SO_3$

  Sulfuric (IV) acid is weakly acidic (4-5), due to the reaction being reversible and the position of the equilibrium being to the left-hand side. 

  $SO_2+$$H_2O\ \leftrightarrow\ H^+$$+$$H_2SO_3$
• Reaction of sulfur trioxide with water:

  Sulfur trioxide reacts very vigorously with water producing sulfuric (VI) acid, which is highly acidic (2-3).

  $SO_2+$$H_2O\ \rightarrow\ H_2SO_4$