Which of the following ions is coloured
$C{u^ + }$
$C{u^{2 + }}$
$T{i^{4 + }}$
${V^{5 + }}$
The number of unpaired electrons is maximum in (Atomic no. : $ Ti = 22; V= 23; Cr = 24; Fe = 26$)
A blue colouration is not obtained when
$Fe,$ $Co$ and $Ni$ have valuable catalytic properties in process involving
$Cu^+$ ion is not stable in aqueous solution, due to
$(a)$ Transition metals can act as catalysts because these can change their oxidation state. How does $Fe(III)$ catalyse the reaction between iodide and persulphate ions ?
$(b)$ Mention any three processes where transition metals act as catalysts.