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5. Co-ordination chemistry — Chemistry STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceChemistry5. Co-ordination chemistry1 Mark
MCQ
Given below are two statements, one is labelled as Assertion $A$ and the other is labelled as Reason $R$.

Assertion $A$ : $\left[ CoCl \left( NH _3\right)_5\right]^{2+}$ absorbs at lower wavelength of light with respect to $\left[ Co \left( NH _3\right)_5\left( H _2 O \right)\right]^{3+}$

Reason $R$ : It is because the wavelength of the light absorbed depends on the oxidation state of the metal ion.

In the light of the above statements, choose the correct answer from the options given below :

  • ✓
    $A$ is false but $R$ is true.
  • B
    $A$ is true but $R$ is false.
  • C
    Both $A$ and $R$ are true and $R$ is the correct explanation of $A$.
  • D
    Both $A$ and $R$ are true and R is NOT the correct explanation of $A$.
✓

Answer

Correct option: A.
$A$ is false but $R$ is true.
a
Since $H _2 O$ is strong field ligand compared to chloride and $Co ^{3+}$ ion is present.

$\therefore$ CFSE is higher for $\left[ Co \left( NH _3\right)_5 H _2 O \right]^{+3}$, hence it will absorb at lower wavelength.

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