Question

Which of the following does not give oxygen on heating ?

• A. KClO₃
• B. Zn(ClO₃)₂
• C. K₂Cr₂O₇
• D. (NH₄)₂Cr₂O₇

Answer 1

The Correct Option is D

To determine which compound does not release oxygen upon heating, let's analyze the decomposition reactions of each given compound:

1. KClO₃ (Potassium chlorate):
   When heated, potassium chlorate decomposes to release oxygen as per the reaction: 2 \text{KClO}_3 \rightarrow 2 \text{KCl} + 3 \text{O}_2.
   This indicates that KClO₃ gives oxygen on heating.
2. Zn(ClO₃)₂ (Zinc chlorate):
   On heating, zinc chlorate decomposes similarly to potassium chlorate: Zn(\text{ClO}_3)_2 \rightarrow ZnCl_2 + 3 \text{O}_2.
   This reaction also produces oxygen.
3. K₂Cr₂O₇ (Potassium dichromate):
   Potassium dichromate, when heated, decomposes to release oxygen: 4 \text{K}_2 \text{Cr}_2 \text{O}_7 \rightarrow 4 \text{K}_2 \text{Cr}_2 \text{O}_4 + 3 \text{O}_2.
   This indicates the release of oxygen from K₂Cr₂O₇.
4. (NH₄)₂Cr₂O₇ (Ammonium dichromate):
   Ammonium dichromate decomposes as follows: (NH_4)_2Cr_2O_7 \rightarrow Cr_2O_3 + N_2 + 4 \text{H}_2\text{O}.
   In this decomposition, nitrogen and water vapor are produced, but oxygen is not released.

Based on the analysis above, the compound that does not release oxygen when heated is (NH₄)₂Cr₂O₇ (Ammonium dichromate).