Among $\mathrm{Al}_{2}\mathrm{O}_{3}$, $\mathrm{SiO}_{2}$, $\mathrm{P}_{2}\mathrm{O}_{3}$ and $\mathrm{SO}_{2}$ the correct order of acid strength is

(B) $\mathrm{Al}_{2}\mathrm{O}_{3}<\mathrm{SiO}_{2}<\mathrm{P}_{2}\mathrm{O}_{3}<\mathrm{SO}_{2}$

(A) $\mathrm{SO}_{2}<\mathrm{P}_{2}\mathrm{O}_{3}<\mathrm{SiO}_{2}<\mathrm{Al}_{2}\mathrm{O}_{3}$

(C) $\mathrm{Al}_{2}\mathrm{O}_{3}<\mathrm{SiO}_{2}<\mathrm{SO}_{2}<\mathrm{P}_{2}\mathrm{O}_{3}$

(D) $\mathrm{SiO}_{2}<\mathrm{SO}_{2}<\mathrm{Al}_{2}\mathrm{O}_{3}<\mathrm{P}_{2}\mathrm{O}_{3}$

JEE Main · 2004 · 24 Apr 2004 · Offline · Classification of Elements and Periodicity

Among

Al_{2} O_{3}

SiO_{2}

P_{2} O_{3}

and

SO_{2}

the correct order of acid strength is

(A) $SO_{2} < P_{2} O_{3} < SiO_{2} < Al_{2} O_{3}$
(B) $Al_{2} O_{3} < SiO_{2} < P_{2} O_{3} < SO_{2}$ ✓ Correct
(C) $Al_{2} O_{3} < SiO_{2} < SO_{2} < P_{2} O_{3}$
(D) $SiO_{2} < SO_{2} < Al_{2} O_{3} < P_{2} O_{3}$

Answer: (B)

Solution

Across a period the oxides move from basic through amphoteric to acidic as the central element grows more electronegative and non-metallic. Here aluminium, silicon, phosphorus and sulphur run left to right, so

Al X_{2} O X_{3}

is amphoteric and least acidic,

SiO X_{2}

weakly acidic,

P X_{2} O X_{3}

more strongly acidic, and

SO X_{2}

the most acidic. Acid strength thus rises in the order

Al X_{2} O X_{3} < SiO X_{2} < P X_{2} O X_{3} < SO X_{2}

JEE Main · 2004 · 24 Apr 2004 · Offline · Single correct option

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JEE Main · 2004 · 24 Apr 2004 · Offline · Classification of Elements and Periodicity

Solution

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