Question

Statement 1:$E^{\circ}$ for $Mn^{3+}/Mn^{2+}$ + is more positive than $Cr^{3+}/Cr^{2+}$
Statement 2:The third ionisation energy of $Mn$ is larger than that of $Cr$

• A. If both Statement $1$ and Statement $2$ are true and the statement $2$ is the correct explanation of the statement $1$
• B. If both Statement $1$ and Statement $2$ are true but statement $2$ is not the correct explanation of the statement $1$
• C. If Statement $1$ is true but Statement $2$ is false
• D. If Statement $1$ is false but Statement $2$ is true

Answer 1

Answer: (B)

It is known that the value of $E^{\circ}$ becomes more negative down the series. As the chromium is present below in electrochemical series than $Mn$, so $Mn$ has more positive $E^{\circ}$ value than $Cr$
$Mn \to 3d^{5}\,4s^{2}$ $Mn^{2+} \to 3d^{5}\,4s^{0}$
$Cr \to 3d^{5}\,4s^{1}, Cr^{2+} \to 3d^{4}\,4s^{0}$
For elimination of one electron from $Mn^{2+}$, more energy is required due to its stable configuration. That is why third Ionisation energy of $Mn$ is larger than $Cr$