Question

Al2O3 is an amphoteric oxide. Which of the following statement(s) are correct for it?
(i)It is soluble in HCl
(ii)It is soluble in NaOH
(iii)It is more basic than CaO
(iv)It is soluble in HBr
Choose the correct statement(s)
A-i,ii
B-i,ii,iv
C-i,ii,iii
D-i,iii

Answer 1

Answer:

corrwct answer is A=i,ii

Answer 2

Solution: The statements which are correct for ammonium oxide are

It is soluble in HCl

It is soluble in NaOH

It is soluble in HBr

So options i) ii) and iv) are correct

• Amphoteric oxide are the oxides that are soluble in both acid and base to produce salt and water

• HCl is an acid so ammonium oxide is soluble in HCl and the reaction is  $Al_{2}O_{3} +6HCl - > 2AlCl_{3} + 3H_{2}O$ so statement i) is correct.
• NaOH is a base so ammonium oxide is soluble in HCl and the reaction is  $Al_{2}O_{3} +2NaOH - > 2NaAlO_{2} + H_{2}O$ so statement ii) is correct.
• As we move from left to right across the periodic table metallic character of the elements decreases. The more metallic character elements has the more basic their oxide is. Hence Aluminum oxide is not basic than CaO so statement iii) is incorrect.
• HBr is also an acid so aluminum oxide is soluble in HBr and the reaction is  $Al_{2}O_{3} +6HBr - > 2AlBr_{3} + 3H_{2}O$ so statement iv) is correct.

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