Question

Among the oxides SiO$_2$, SO$_2$, Al$_2$O$_3$, and P$_2$O$_5$, the correct order of acidic strength is:

• A. $\text{SiO}_2<\text{SO}_2<\text{Al}_2\text{O}_3<\text{P}_2\text{O}_5$
• B. $\text{SO}_2<\text{P}_2\text{O}_5<\text{Al}_2\text{O}_3<\text{SiO}_2$
• C. $\text{Al}_2\text{O}_3<\text{SiO}_2<\text{P}_2\text{O}_5<\text{SO}_2$
• D. $\text{Al}_2\text{O}_3<\text{P}_2\text{O}_5<\text{SiO}_2<\text{SO}_2$

Hint:

The acidity of oxides increases with the electronegativity of the central atom in non-metal oxides.

Answer 1

The Correct Option is C

The acidic strength of these oxides increases from Al$_2$O$_3$ (amphoteric) to SiO$_2$ (weakly acidic) to P$_2$O$_5$ (strongly acidic) and then to SO$_2$ (more acidic due to its ability to form sulfurous acid upon hydration).