Chemistry Electrochemistry UHS 2024
PMDC Verified Question 1 of 73
Oxidation number of 'Mn' in \( KMnO_4 \) is:
A
0
B
1
C
-7
D
7
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: 7
Concept:

For a neutral chemical compound, the algebraic sum of all the individual oxidation numbers must equal zero.

Formula:

$$+1 + x + 4(-2) = 0$$

Solution:

  • Potassium (K) is a Group 1 metal and always has an oxidation state of \( +1 \).


  • Oxygen (O) typically has an oxidation state of \( -2 \).


  • Let \( x \) be the oxidation state of Manganese (Mn).


  • Set up the equation: \( 1 + x - 8 = 0 \).


  • Solve for \( x \): \( x - 7 = 0 \implies x = +7 \).


Why other options are incorrect:

Manganese can exist in \( +2, +3, +4, +6 \) states, but in the highly oxidized permanganate ion, it is stripped of 7 valence electrons, resting at \( +7 \).

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