Question

Which of the following is a correct statement?

• A. Aqueous solutions of $Cu ^{+}$ and $Zn ^{2+}$ are colourless
• B. Aqueous solutions of $Cu ^{2+}$ and $Zn ^{2+}$ are colourless
• C. Aqueous solution of $Fe ^{3+}$ is green in colour
• D. Aqueous solution of $MnO _{4}^{-}$ is colourless

Answer 1

Answer: (A)

(a) $Cu ^{+}=[ Ar ] 3 d^{10}$

(No unpaired electrons, so it is colourless)
$Zn ^{2+}=[Ar] 3 d^{10}$
(No unpaired electrons, so it is colourless)
(b) $Cu ^{2+}=[ Ar ] 3 d^{9}$

(One unpaired electron is present, so it is coloured)
$Zn ^{2+}$ is colourless.
(c) The colour of $Fe ^{2+}$ is green while that of $Fe ^{3+}$ is blue.
(d) $MnO _{4}^{-}$ contains no unpaired electrons, however, it is coloured due to charge transfer.