MCQ practice · SSC Chemistry Board questions · Chapter 7: Chemical Reactions
In the reaction Mg(NO₃)₂ -Δ→ MgO + A + O₂, the formula of compound 'A' is:
Think it through first, then pick an option.
- a NO₂
- b N₂O₃
- c NO
- d N₂
Answer and explanation
Correct answer: a NO₂
Mg(NO₃)₂ breaks down on heating into MgO, NO₂ and O₂: 2Mg(NO₃)₂ → 2MgO + 4NO₂ + O₂. So A is NO₂, a brown gas.
Why the other options are wrong
- b N₂O₃: N₂O₃ is not formed when a nitrate decomposes; N is +5 in Mg(NO₃)₂, and the gas obtained is NO₂ (N +4).
- c NO: N is +2 in NO; heating Mg(NO₃)₂ gives NO₂, not NO.
- d N₂: N₂ is an elemental gas; heating Mg(NO₃)₂ does not free nitrogen, it gives NO₂.
More board questions on this topic
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- In which reaction does electron transfer occur?
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