Question

Assertion :E${}^0$ for Mn${}^{3+}$/Mn${}^{2+}$ is more positive than Cr${}^{3+}$/Cr${}^{2+}$ Reason: The third ionisation energy of Mn is larger than that of Cr.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

E${}^0$ for Mn${}^{3+}$/Mn${}^{2+}$ is more positive than Cr${}^{3+}$/Cr${}^{2+}$, because of required change from d${}^5$ (half-filled) to d${}^4$ (partially filled) in case of Mn and this required higher energy.

$E^{0}C{r}^{3+}/C{r}^{2+}=-0.41V$

$E^{0}M{n}^{3+}/M{n}^{2+}=+1.57V$

Thus, Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Hence, the correct option is $\text{A}$