Question

Among $A{l}_2{O}_3,Si{O}_2,P_2{O}_3$ and $S{O}_2$ the correct order of acid strength is:

• A. $S{O}_2<P_2{O}_3<Si{O}_2<{Al}_2{O}_3$
• B. $Si{O}_2<S{O}_2<{Al}_2{O}_3<P_2{O}_3$
• C. $A{l}_2{O}_3<Si{O}_2<S{O}_2<P_2{O}_3$
• D. ${Al}_2{O}_3<Si{O}_2<P_2{O}_3<S{O}_2$

Answer 1

The correct option is D ${Al}_2{O}_3<Si{O}_2<P_2{O}_3<S{O}_2$

The oxides given are 3rd period oxides,so as we go from left to right in a period acidic strength of oxides will be increases as size decreases.

$A{l}_2{O}_3$ is amphoterric,$Si{O}_2$ is slightly acidic whereas $P_2{O}_3$ and $S{O}_2$ are anhydrides of acid $H_{3}P{O}_3$ and $H_{2}S{O}_3$.

So the correct order of acidic strength oxides of 3rd period elements is $A{1}_2{O}_3<Si{O}_2<P_2{O}_3<S{O}_2$

Hence option D is correct.