Question

Which oxide of manganese is amphoteric?
(a)- $Mn{{O}_{2}}$
(b)- $M{{n}_{2}}{{O}_{3}}$
(c)- $M{{n}_{2}}{{O}_{7}}$
(d)- $MnO$

Answer 1

Amphoteric means the given compound can react with acid as a base and it can react with a base as acid. So, the compounds given in the options are of manganese, as the oxidation states of manganese range from +2 to +7. If the compound has a manganese oxidation state in the oxidation state +4, then it can act as amphoteric.

Complete answer:
A compound can be differentiated into different types like acids, bases, neutral, and amphoteric. We generally know acids, bases, and neutrals but amphoteric means the given compound can react with acid as a base and it can react with a base as acid.
So, the compounds given in the options are of manganese, as the oxidation states of manganese range from +2 to +7. If the compound has a manganese oxidation state in the oxidation state +4, then it can act as amphoteric.
Now, let us calculate the oxidation state of manganese in all the compounds given in the options. All the compounds in the options are made up of manganese and oxygen atoms, and the oxidation state of oxygen is -2.
(a)- $Mn{{O}_{2}}$
Let the oxidation of manganese is x.
$x+2(-2)=0$
$x=+4$
(b)- $M{{n}_{2}}{{O}_{3}}$
Let the oxidation state of manganese is x.
$2x+3(-2)=0$
$2x-6=0$
$x=+3$
(c)- $M{{n}_{2}}{{O}_{7}}$
Let the oxidation state of manganese is x.
$2x+7(-2)=0$
$2x-14=0$
$x=+7$
(d)- MnO
Let the oxidation state of manganese is x.
$x+(-2)=0$
$x=+2$
So, from the given compounds, $Mn{{O}_{2}}$ has a +4 oxidation state. Hence it will act as amphoteric.

Therefore, the correct answer is option (a)- $Mn{{O}_{2}}$

Note:
In $M{{n}_{2}}{{O}_{7}}$, the oxidation state of manganese is +7 which means the oxidation state is high so, it is an acidic oxide. In MnO, the oxidation state of manganese is +2 which means the oxidation state is low so it is a basic oxide.