Coloured salts are formed by

Which one of the following ions will be colourless in an aqueous solution? (Atomic numbers: $Sc = 21, Fe = 26, Ti = 22, Mn = 25$)

Which pair of ions gives a blue colour in an aqueous state?
$V^{+4}, Ni^{+2}, Ti^{+3}, Co^{+2}, Fe^{+3}, Cu^{+2}$

Assertion : Borax bead test is not suitable for $Al(III)$.
Reason : $Al_2O_3$ is insoluble in water.

Silver atom has completely filled $d$ orbitals $\left(4d^{10}\right)$ in its ground state. How can you say that it is a transition element?

For $M^{2+} / M$ and $M^{3+} / M^{2+}$ systems,the ${E^{\Theta}}$ values for some metals are as follows:
$Cr^{2+} / Cr : -0.9 \ V$
$Cr^{3+} / Cr^{2+} : -0.4 \ V$
$Mn^{2+} / Mn : -1.2 \ V$
$Mn^{3+} / Mn^{2+} : +1.5 \ V$
$Fe^{2+} / Fe : -0.4 \ V$
$Fe^{3+} / Fe^{2+} : +0.8 \ V$
Use this data to comment upon:
$(i)$ The stability of $Fe^{3+}$ in acid solution as compared to that of $Cr^{3+}$ or $Mn^{3+}$ and
$(ii)$ The ease with which iron can be oxidised as compared to a similar process for either chromium or manganese metal.