Question

What is the oxidation number of Manganese (Mn) in the compound \( KMnO_4 \)?

• A. \(+4\)
• B. \(+6\)
• C. \(+7\)
• D. \(+2\)

Hint:

In most compounds oxygen has oxidation number \( -2 \), which helps quickly determine the oxidation state of the central atom.

Answer 1

The Correct Option is C

Concept: The sum of oxidation numbers of all atoms in a neutral compound is zero. Key oxidation states:
• Potassium \(K = +1\)
• Oxygen \(O = -2\)

Step 1: Assign oxidation numbers. For \( KMnO_4 \): \[ K = +1 \] \[ O = -2 \quad (\text{for each oxygen atom}) \] There are 4 oxygen atoms: \[ 4 \times (-2) = -8 \] Let the oxidation number of Mn be \(x\).

Step 2: Apply the sum rule. \[ (+1) + x + (-8) = 0 \] \[ x -7 = 0 \] \[ x = +7 \]