Question

Among the following oxides of 3d elements, the number of mixed oxides are ____________.
\[ \mathrm{Ti_2O_3,\ V_2O_4,\ Cr_2O_3,\ Mn_3O_4,\ Fe_3O_4,\ Fe_2O_3,\ Co_3O_4} \]

Hint:

Mixed oxides usually have formulas like \(M_3O_4\) and can be written as a combination of two simpler oxides.

Answer 1

Correct Answer: 3

The task is to identify the mixed oxides from the given list of 3d element oxides. Mixed oxides contain more than one oxidation state of the same metal in a single compound.
To determine this, we will assess the oxidation states in each compound:

• Ti₂O₃: Titanium has a single oxidation state of +3 here without mixing.
• V₂O₄: Vanadium has an oxidation state of +4 for both atoms (not a mixed oxide).
• Cr₂O₃: Chromium is in a +3 oxidation state only.
• Mn₃O₄: Manganese oxidation states are +2 and +3, indicating a mixed oxide.
• Fe₃O₄: Known as magnetite, iron is in +2 and +3 oxidation states, making it a mixed oxide.
• Fe₂O₃: Iron is exclusively in the +3 oxidation state.
• Co₃O₄: Cobalt exhibits +2 and +3 oxidation states, confirming it as a mixed oxide.

From this analysis, the mixed oxides are Mn₃O₄, Fe₃O₄, and Co₃O₄. Thus, the total count of mixed oxides is 3. This value falls within the given range of 3,3, confirming accuracy.