MCQ
Which of the following equation is not correct?
  • A
    $2 \mathrm{AgBr}(\mathrm{s})+\text { Sunlight } \rightarrow 2 \mathrm{Ag}(\mathrm{s})+\mathrm{Br}_2(\mathrm{~g})$
  • $\mathrm{FeSO}_4(\mathrm{~s})+\mathrm{Cu}(\mathrm{aq}) \rightarrow \mathrm{CuSO}_4(\mathrm{aq})+\mathrm{Fe}(\mathrm{s})$
  • C
    $\mathrm{Pb}(\mathrm{s})+\mathrm{CuCl}_2(\mathrm{aq}) \rightarrow \mathrm{PbCl}_2(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})$
  • D
    $\mathrm{Zn}(\mathrm{s})+\mathrm{CuSO}_4(\mathrm{aq}) \rightarrow \mathrm{ZnSO}_4(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})$

Answer

Correct option: B.
$\mathrm{FeSO}_4(\mathrm{~s})+\mathrm{Cu}(\mathrm{aq}) \rightarrow \mathrm{CuSO}_4(\mathrm{aq})+\mathrm{Fe}(\mathrm{s})$
The equation $\mathrm{FeSO}_4(\mathrm{~s})+\mathrm{Cu}(\mathrm{aq}) \rightarrow \mathrm{CuSO}_4(\mathrm{aq})+\mathrm{Fe}(\mathrm{s})$ is incorrect.
Because $\ce{Fe}$ is highly recative compared to $\ce{Cu}$ and hence $\ce{Cu}$ cannot replace $\ce{Fe}$ from its solution.
$\mathrm{Fe}(\mathrm{s})+\mathrm{CuSO}_4(\mathrm{aq}) \rightarrow \mathrm{FeSO}_4(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})$

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