Chemistry S & P Block Elements DUHS 2023
PMDC Verified Question 41 of 104
Superoxide of group IA element (M) has formula:
A
\( \text{M}_2\text{O} \)
B
\( \text{M}_2\text{O}_3 \)
C
\( \text{MO}_2 \)
D
\( \text{M}_2\text{O}_2 \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: \( \text{MO}_2 \)
Concept:

To determine the formula of a compound, we balance the charge of the metal cation with the charge of the specific oxygen anion.

Solution:

  • A Group IA element (let's call it M) always forms a cation with a +1 charge: \( \text{M}^+ \).
  • The superoxide polyatomic ion has a collective charge of -1 spread over two oxygen atoms: \( \text{O}_2^- \).
  • To form a neutral compound, one \( \text{M}^+ \) ion perfectly balances one \( \text{O}_2^- \) ion.
  • Applying the criss-cross method (1:1 ratio), the general formula is \( \text{MO}_2 \) (e.g., \( \text{KO}_2 \)).


Why other options are incorrect:

  • \( \text{M}_2\text{O} \): Normal oxide.
  • \( \text{M}_2\text{O}_2 \): Peroxide.
  • \( \text{M}_2\text{O}_3 \): Incorrect valency for Group I.

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