Question

What is the difference in oxidation number of Mn in \(\text{KMnO}_4\) and \(\text{MnO}_2\) ?

• A. 1
• B. 3
• C. 4
• D. 5

Hint:

In \(\text{KMnO}_4\), Mn is usually \(+7\), and in \(\text{MnO}_2\), Mn is usually \(+4\). These are common oxidation states worth remembering.

Answer 1

The Correct Option is B

Concept:
Oxidation number is found by using the rule that the sum of oxidation numbers in a neutral compound is zero.

Step 1: Find oxidation number of Mn in \(\text{KMnO}_4\).
Let oxidation number of Mn be \(x\). \[ (+1) + x + 4(-2) = 0 \] \[ 1 + x - 8 = 0 \] \[ x = +7 \]

Step 2: Find oxidation number of Mn in \(\text{MnO}_2\).
Let oxidation number of Mn be \(y\). \[ y + 2(-2) = 0 \] \[ y - 4 = 0 \] \[ y = +4 \]

Step 3: Find the difference.
\[ 7 - 4 = 3 \] Hence, the correct answer is:
\[ \boxed{(B)\ 3} \]