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EEJ MAIN Chemistry QUESTION #7148
Question 1
What are the primary oxides produced when Lithium ($Li$), Sodium ($Na$), and Potassium ($K$) are burned in an excess of air, respectively?
  • $LiO_{2}$, $Na_{2}O_{2}$ and $K_{2}O$
  • $Li_{2}O_{2}$, $Na_{2}O_{2}$ and $KO_{2}$
  • $Li_{2}O$, $Na_{2}O_{2}$ and $KO_{2}$✔️
  • $Li_{2}O$, $Na_{2}O$ and $KO_{2}$
Correct Answer Explanation
When burned in excess air:
  • Lithium forms the normal oxide ($Li_{2}O$).
  • Sodium forms the peroxide ($Na_{2}O_{2}$).
  • Potassium (and larger alkali metals) forms the superoxide ($KO_{2}$).
This variation is due to the increasing size of the cation stabilizing larger anions.