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Which one of the following is not an example of calcination ?

1. CaCO 3 ⎯→ ⎯ Δ CaO + CO 2
2. Fe 2 O 3 . xH 2 O ⎯→ ⎯ Δ Fe 2 O 3 + xH 2 O
3. 2PbS + 3O 2 ⎯→ ⎯ Δ 2PbO + 2SO 2
4. CaCO 3 . MgCO 3 ⎯→ ⎯ Δ CaO + MgO + 2CO 2

Correct answer: 2PbS + 3O 2 ⎯→ ⎯ Δ 2PbO + 2SO 2

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