Question

The number of terminal oxygen atoms present in the product B obtained from the following reaction is ______.
FeCr₂O₄ + Na₂CO₃ + O₂ → A + Fe₂O₃ + CO₂
A + H⁺ → B + H₂O + Na⁺

Answer 1

Correct Answer: 6

To solve this problem, we need to follow the given chemical reactions step-by-step and identify the number of terminal oxygen atoms in product B.
First, consider the initial reaction:
FeCr₂O₄ + Na₂CO₃ + O₂ → A + Fe₂O₃ + CO₂
In this reaction, sodium carbonate (Na₂CO₃) and oxygen are likely oxidizing the chromium component to form sodium chromate (Na₂CrO₄), while iron forms hematite (Fe₂O₃). Thus, A can be inferred as Na₂CrO₄.
Next, A reacts with H⁺:
Na₂CrO₄ + H⁺ → B + H₂O + Na⁺
This reaction suggests the formation of dichromic acid, ultimately yielding chromate (CrO₄^2-) converting to dichromate (Cr₂O₇^2-) under acidic conditions:
2 CrO₄^2- + 2 H⁺ → Cr₂O₇^2- + H₂O
Hence, B is Cr₂O₇^2- (dichromate ion).
Dichromate (Cr₂O₇^2-) has a structure where each chromium atom is bonded to three oxygen atoms and shares an oxygen atom between them (bridging oxygens). The structure is as follows:
O₃Cr-O-CrO₃
Total terminal oxygen atoms = 3 (from one Cr) + 3 (from the other Cr) = 6.
Thus, the number of terminal oxygen atoms in the dichromate ion Cr₂O₇^2- is 6.
This value falls within the given range of 6,6.