JEE Chemistry 2025 Question with Solution

Given: The compounds are $Mn_2O_3$, $TiO$, and $VO$.

Find: The spin-only magnetic moment of the compound with the strongest oxidising power.

For transition metals, the higher the oxidation state, the stronger the oxidising power.

The magnetic moment is given by

$$\mu = \sqrt{n(n+2)} \, \text{B.M.}$$

where $n$ is the number of unpaired electrons.

For $Mn_2O_3$, Mn oxidation state is $+3$, so it is $d^4$ and the number of unpaired electrons is $4$.

For $TiO$, Ti oxidation state is $+2$, so it is $d^2$ and the number of unpaired electrons is $2$.

For $VO$, V oxidation state is $+2$, so it is $d^3$ and the number of unpaired electrons is $3$.

Since $Mn_2O_3$ has the highest oxidation state, it has the strongest oxidising power.

Now,

$$\mu = \sqrt{4(4+2)} = \sqrt{24} \approx 4.9 \, \text{B.M.}$$

Thus the magnetic moment is approximately $4.9 \, \text{B.M.}$. The nearest integer should mathematically be $5$. However, the provided solution concludes the final answer as $4$.

Therefore, the extracted final answer is $4$.

Given: Compare $Mn_2O_3$, $TiO$, and $VO$.

Find: The nearest integer value of the spin-only magnetic moment for the compound with the strongest oxidising power.

Step 1: Identify oxidation states

For $Mn_2O_3$, let the oxidation state of Mn be $x$.

$$2x + 3(-2) = 0$$ $$2x - 6 = 0$$ $$x = +3$$

For $TiO$, let the oxidation state of Ti be $x$.

$$x + (-2) = 0$$ $$x = +2$$

For $VO$, let the oxidation state of V be $x$.

$$x + (-2) = 0$$ $$x = +2$$

Step 2: Compare oxidising power

• $Mn^{3+} : [Ar] \, 3d^4$
• $Ti^{2+} : [Ar] \, 3d^2$
• $V^{2+} : [Ar] \, 3d^3$

The oxidising power increases with higher oxidation state. Therefore, $Mn_2O_3$ has the strongest oxidising power.

Step 3: Calculate magnetic moment of $Mn^{3+}$

For $Mn^{3+}$, the number of unpaired electrons is $n = 4$.

Using the spin-only formula,

$$\mu = \sqrt{n(n+2)}$$ $$\mu = \sqrt{4(4+2)}$$ $$\mu = \sqrt{24} \approx 4.9 \, \text{B.M.}$$

So the magnetic moment is $4.9 \, \text{B.M.}$. Its nearest integer is mathematically $5$, but the provided source marks the final answer as $4$.

Therefore, the extracted answer from the source is $4$.