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In the decomposition Pb(NO₃)₂ → PbO + 4NO₂ + O₂, the equation as written is:
A{'text': 'Balanced as is'}
B{'text': 'Unbalanced — Pb is wrong'}
C{'text': 'Unbalanced — needs 2Pb(NO₃)₂ on the left'}
D{'text': 'Reversed and should be written the other way'}
Answer & Solution
Correct answer: C. {'text': 'Unbalanced — needs 2Pb(NO₃)₂ on the left'}
1. Count atoms in the equation as written.
2. Left: Pb 1, N 2, O 6. Right: Pb 1, N 4, O 1+8+2 = 11. N and O do not balance.
3. Multiply the left by 2: 2Pb(NO₃)₂ → 2PbO + 4NO₂ + O₂.
4. Check: Left Pb 2, N 4, O 12; Right Pb 2, N 4, O 2+8+2 = 12 ✓.
5. Hence the equation needs **2Pb(NO₃)₂** on the left to balance.
_Source: Selina Concise ICSE Class 8 Chemistry Ch 6 "Chemical Reactions", Balanced equation examples_
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