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

Answer 1

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

Across the period, the electronegativity values increase on account of decreasing size of atoms and increasing nuclear charge. Hence, basic character of oxides decreases and acidic character of oxides increases and acidic character of oxides increases from left to right in a period.
$\stackrel{+3}{A{l}_2}{O}_3<\stackrel{+4}{Si}{O}_2<\stackrel{+3}{P_2}{O}_3<\stackrel{+4}{S}{O}_2$
$A{l}_2{O}_3$ is amphoteric. $Si{O}_2$ is slightly acidic whereas $P_2{O}_3$ and $S{O}_2$ are the anhydrides of the acids $H_{3}P{O}_3$ and $H_{2}S{O}_3$ respectively