The aqueous solution of transition metal salt changes colour from pink to blue, when concentrated hydrochloric acid is added to it. The change In colour is due to

  • A

    evolution of hydrogen that changes the oxidation state of the metal ion

  • B

    change in the coordination number of the metal ion from $6$ to $4$ and formation of new species in solution

  • C

    formation of a coordination complex of the metal ion with hydrochloric acid

  • D

    protonation of the metal ion

Similar Questions

Which of the following element has maximum density

Iron becomes passive by ..................... due to formation of .....................

In $d-$ block $3d$ series, which of the following element has maximum size ?

$MnO _4^{-}$oxidises $(i)$ oxalate ion in acidic medium at $333\, K$ and $(ii)$ $HCl$. For balanced chemical equations, the ratios $\left[ MnO _4^{-}: C _2 O _4^{2-}\right]$ in $(i)$ and $\left[ MnO _4^{-}: HCl \right]$ in $(ii)$ respectively are

  • [KVPY 2011]

Passing $H_2S$ gas into a mixture of $Mn^{+2}, Ni^{+2}, Cu^{+2}$ and $Hg^{2+}$ ions in an acidified aqueous solution precipitates