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.
$(i)$ The ${E^\Theta }$ value for $Fe ^{3+} / Fe ^{2+}$ is higher than that for $Cr ^{3+} / Cr ^{2+}$ and lower than that for $Mn ^{3+} / Mn ^{2+} . So ,$ the reduction of $Fe ^{3+}$ to $Fe ^{2+}$ is easier than the reduction of $Mn ^{3+}$ to $Mn ^{2+},$ but not as easy as the reduction of $Cr ^{3+}$ to $Cr ^{2+}$. Hence, $Fe ^{3+}$ is more stable than $Mn ^{3+},$ but less stable than $Cr ^{3+}$. These metal ions can be arranged in the increasing order of their stability as: $Mn ^{3+}\,< \,Fe ^{3+}\,<\, Cr ^{3+}$
$(ii)$ The reduction potentials for the given pairs increase in the following order.
$Mn ^{2+} / Mn \,<\, Cr ^{2+} / Cr \,<\, Fe ^{2+} / Fe$
So, the oxidation of $Fe$ to $Fe ^{2+}$ is not as easy as the oxidation of $Cr$ to $Cr ^{2+}$ and the oxidation of $Mn$ to $Mn ^{2+}$. Thus, these metals can be arranged in the increasing order of their ability to get oxidised as: $Fe \,<\, Cr \,<\, Mn$
Nickel steel contain $\%$ of $ Ni$
Most stable compound among the following is
Copper displaces which of the metal from their salt solutions
Which one of the following does not correctly represent the order of property indicated against it
Although $\mathrm{Cr}^{3+}$ and $\mathrm{Co}^{2+}$ ions have same number of unpaired electrons but the magnetic moment of $\mathrm{Cr}^{3+}$ is $3.87$ $B.M.$ and that of $\mathrm{Co}^{2+}$ is $4.87$ $B.M.$ Why ?