Question

13.which one of the following is different from the others

A. Na2O C. CrO3
B. MgO D. k2O

Answer 1

All the compounds proposed are oxides: Na₂O, CrO₃, MgO and K₂O. The oxides can be classified into amphoteric, acidic, basic or neutral. Among the oxides listed, Na₂O, MgO and K₂O are basic oxides and react with water with formation of bases:

Na₂O + H₂O $\rightarrow$ 2NaOH

MgO + H₂O $\rightarrow$ Mg(OH)₂

K₂O + H₂O $\rightarrow$ 2KOH.

On the contrary, chromium trioxide CrO₃ is different from the others. It is an acidic oxide and it reacts with water with formation of chromic acid:

CrO₃ + H₂O $\rightarrow$ H₂CrO₄.

Answer: C. CrO₃ is different from the others