Zr ($Z = 40$) and Hf ($Z = 72$) have similar atomic and ionic radii because of:

The $E^\circ$ value for the $Mn^{3+}/Mn^{2+}$ couple is more positive than that of $Cr^{3+}/Cr^{2+}$ or $Fe^{3+}/Fe^{2+}$ due to change of:

The catalytic activity of transition metals is due to:

The manganate and permanganate ions are tetrahedral, due to:

The incorrect statement among the following is:

When neutral or faintly alkaline $KMnO_4$ is treated with potassium iodide, iodide ion is converted into 'X'. 'X' is:

Identify the incorrect statement among the following:

Acidified $K_2Cr_2O_7$ solution turns green when $Na_2SO_3$ is added to it. This is due to the formation of:

Which of the following ions will exhibit colour in aqueous solutions?