Question

Answer the following question:
(a) What happens when a dilute acid reacts with a metal oxide? Explain with the help of an example.
(b) Are there any metal oxides that react with both acids and bases? If yes, give an example.
[3 Marks]

Answer 1

(a) Metal oxides are basic in nature. Acids react with metal oxides to form salt and water.
Example: Dilute sulphuric acid reacts with calcium oxide to form calcium sulphate and water.
$CaO\left(s\right)+H_{2}S{O}_4\left(aq\right)\to CaS{O}_4\left(aq\right)+H_{2}O\left(l\right)$
Salt Water
[1 Mark]

(b) Yes, there are a few oxides of amphoteric metals such as zinc and aluminium which react with acids as well as bases.
Reaction with acid:
$A{l}_2{O}_3\left(s\right)+6HCl\left(aq\right)\to 2AlC{l}_3\left(aq\right)+3H_{2}O\left(l\right)$
Acid
[1 Mark]

Reaction with base:
$A{l}_2{O}_3\left(s\right)+2NaOH\left(aq\right)\to 2NaAl{O}_2\left(aq\right)+H_{2}O\left(l\right)$
Base
[1 Mark]