Q10 / 66 · JEE Advanced 2008 (Paper 2) · Chemistry

Statement $\mathbf{1}\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_5 \mathrm{NO}\right] \mathrm{SO}_4$ is paramagnetic. Statement 2 The $\mathrm{Fe}$ in $\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_5 \mathrm{NO}\right] \mathrm{SO}_4$ has three unpaired electrons.

  • Correct answer
    A
    Statement 1 is true, Statement 2 is true, Statement 2 is a correct explanation for Statement 1.
  • B
    Statement 1 is true, Statement 2 is true, Statement 2 is not a correct explanation for Statement 1.
  • C
    Statement 1 is true, Statement 2 is false.
  • D
    Statement 1 is false, Statement 2 is true

Solution

The oxidation number of $\mathrm{Fe}$ in the complex, $\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_5 \mathrm{NO}\right] \mathrm{SO}_4$ is $+1$ [ $\mathrm{NO}$ has $+1$ charge ] $$ \mathrm{Fe}^{+}=[\mathrm{Ar}] 3 d^6 4 s^1 $$ $\mathrm{NO}^{+}$causes pairing of 4 s electron inside . Thus, the configuration is $3 d^7$ and number of unpaired electrons $=3$

Hence, the correct answer is option: 'A'.

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