Ferrous sulphate on heating gives

A blue colouration is not obtained when

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.

Effective magnetic moment of $S{c^{ + 3}}$ ion is

Why is the ${E^\Theta }$ value for the $Mn ^{3+} / Mn ^{2+}$ couple much more positive than that for $Cr ^{3+} / Cr ^{2+}$ or $Fe ^{3+} / Fe ^{2+} ?$ Explain.

Which of the following graph is correct representation between atomic number $(Z)$ and magnetic moment of $d-block$ elements? [Outer electronic configuration : $(n -1)d^x\, ns^{1\, or \,2}$]