Question

The option(s) with only amphoteric oxides is (are):
a.) $C{r}_2{O}_3$, BeO, SnO, $Sn{O}_2$
b.) $C{r}_2{O}_3$, CrO, SnO, PbO
c.) ZnO, $A{l}_2{O}_3$, PbO, $Pb{O}_2$
d.) NO, $B_2{O}_3$, PbO, $Sn{O}_2$

Answer 1

Hint: The amphoteric oxides are the one which have properties of both acidic and basic oxides. So, the option which will contain all those molecules which are amphoteric in nature will be the correct answer. Here are two options that will show such molecules.

Complete step by step answer:
For this, one should first know what are amphoteric oxides. If we know the basic concepts then it is always easy to find out from the options given. So, let us first see the amphoteric oxides.
As the word amphoteric means dual properties. So, the amphoteric oxides are the molecules which have properties of both acidic oxides and basic oxides. These molecules can react with both acids as well as bases to form salt and water.
The amphoteric oxides show such a dual character because of their oxidation states. Generally, the amphoteric oxides belong to group 2- the alkaline earth metals and transition metals.
Now, let us see the options given to us.
The first molecule given to us is $C{r}_2{O}_3$, This molecule has chromium in +3 oxidation state. It is amphoteric in nature. The chromium can achieve lower and higher both oxidation states. This compound reacts with both acids and bases to give salt and water. Thus, it is amphoteric in nature.
The next molecule given is BeO, This Be has more electronegativity than lithium and further the Be-O bond is covalent in nature. This molecule lies on the borderline between acids and bases. So, it shows amphoteric behaviour.
The third molecule is SnO, The tin oxide is amphoteric in nature because it can react with acids and bases both forming water and salt.
The fourth molecule is $Sn{O}_2$. The $Sn{O}_2$ reacts with both acids and bases to form water and salt. Thus, it is also amphoteric in nature.
The next molecule is CrO. This oxide is basic in nature with chromium having +2 oxidation state.
After this, the other molecule is PbO. The lead oxide is amphoteric in nature because it can react with both acids and bases to form salt and water.
The next molecule is ZnO. The Zinc oxide is also amphoteric in nature because it reacts with acids and bases both to form salt and water.
The next molecule is $A{l}_2{O}_3$, This aluminium oxide is also amphoteric in nature.
After this we have $Pb{O}_2$ which is also amphoteric in nature.

The NO molecule is neutral oxide. Such an oxide does not show properties of acidic and basic oxides.
After this the $B_2{O}_3$ molecule is actually an anhydride, It reacts with the water forming boric acid which is acidic in nature. Thus, it is categorised under acidic oxides.
The option a.) and option c.) contains all the molecules which are amphoteric in nature. So, these will be correct answers.
So, the correct answer is “Option A and C”.

Note: One should not get confused with neutral oxides and amphoteric oxides. The amphoteric oxides show properties of both acidic as well as basic oxides while the neutral oxides do not show the properties of acidic and basic oxides.