Question

Oxidation states of the metal in the minerals haematite and magnetite, respectively are:
(A) (II), (III) in haematite and (III) in magnetite
(B) (II), (III) in haematite and (II) in magnetite
(C) (II) in haematite and (II), (III) in magnetite
(C) (III) in haematite and (II), (III) in magnetite

Answer 1

Iron is the metal that is present in both the minerals haematite and magnetite. In both the minerals, there are two elements present: iron and oxygen. The magnetite mineral has two oxidation states.

Complete step by step solution:
We know that metals are extracted from their minerals for commercial production. Iron is an element that belongs to the d-block and it is found in many minerals such as haematite, limonite, magnetite, siderite, and iron pyrates. The most important of these are haematite and magnetite.
Haematite ore is also known as red oxide of iron and the formula of haematite ore is $F{{e}_{2}}{{O}_{3}}$. So, the oxidation state of iron in $F{{e}_{2}}{{O}_{3}}$ is:
$2x+3(-2)=0$
$\Rightarrow x=+3$
So, the oxidation state of iron in hematite ore or $F{{e}_{2}}{{O}_{3}}$ is +3 (III).
Now the magnetite ore is also known as magnetic oxide of iron and the formula of magnetite ore is $F{{e}_{3}}{{O}_{4}}$. But the actual formula of magnetite exists as $F{{e}_{2}}{{O}_{3}}.FeO$. So there are two oxidation states of iron in magnetite ore. The first oxidation state of iron:
$2x+3(-2)=0$
$\Rightarrow x=+3$
The second oxidation state of iron is:
$x-2=0$
$\Rightarrow x=+2$
So, the oxidation states of iron in magnetite are +2 and +3.

Therefore, the correct answer is an option (D)- (III) in haematite, and (II), (III) in magnetite.

Note: The oxidation state of iron in its limonite ore having formula $F{{e}_{2}}{{O}_{3}}.2{{H}_{2}}O$ is +3. The oxidation state of iron in its Siderite ore having formula $FeC{{O}_{3}}$ is +2. The oxidation state of iron in its iron pyrites ore having formula $Fe{{S}_{2}}$ is +2.