The following oxides are basic with water EXCEPT:

The following oxides are basic with water EXCEPT:

• A. FeO
• B. SO2
• C. Na2O
• D. CuO

Answer: (B)

Oxides can act as bases when they form hydroxides in water, typically metal oxides. Metal oxides like sodium oxide dissolve in water to give NaOH, a basic solution, so they are basic with water. Iron(II) oxide and copper(II) oxide do the same, forming Fe(OH)2 and Cu(OH)2, respectively, which are basic (though sometimes sparingly soluble). Sulfur dioxide, on the other hand, is a nonmetal oxide and reacts with water to form sulfurous acid, H2SO3, making the solution acidic rather than basic. That acidic behavior is why this oxide is the exception.

Oxides can act as bases when they form hydroxides in water, typically metal oxides. Metal oxides like sodium oxide dissolve in water to give NaOH, a basic solution, so they are basic with water. Iron(II) oxide and copper(II) oxide do the same, forming Fe(OH)2 and Cu(OH)2, respectively, which are basic (though sometimes sparingly soluble). Sulfur dioxide, on the other hand, is a nonmetal oxide and reacts with water to form sulfurous acid, H2SO3, making the solution acidic rather than basic. That acidic behavior is why this oxide is the exception.