Question

Assertion :Acidified $\left[Cu\right(N{H}_3{)}_4{]}^{2+}$ and $\left[Cu\right(H_{2}O{)}_4{]}^{2+}$ both react with $K_4\left[Fe\right(CN{)}_6]$ to give brown ppt. Reason: Both complexes are blue in colour of little different shade.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

$C{u}^{2+}$ ions react with $K_4\left[Fe\right(CN{)}_6]$ to form chocolate brown precipitate of $C{u}_2\left[Fe\right(CN{)}_6]$.
$2C{u}^{2+}+K_4\left[Fe\right(CN{)}_6]\to \underset{chocolatebrownppt}{C{u}_2\left[Fe\right(CN{)}_6]}+4K^{+}$
In both the complexes, the oxidation state of copper is same and contains same number of electrons. Only one unpaired electron is present in both complexes.
Hence, they have same blue colour. Since, the strength of ligands is different, they have different shades.
Thus, Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.