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JAMB Chemistry 1980 Question 19

Question 19

Atomic Structure

Element X has a total of 19 electrons and can react with oxygen to form an oxide. Which of the following statements is NOT true of the oxide of the element?

  1. A.When exposed to air, it slowly changes to liquid.
  2. B.Its solution in water conducts electricity
  3. C.Its solution in water, on evaporation, gives a white solid
  4. D.Its solution in water liberates hydrogen when in contact with aluminium metal
  5. E.Its oxide, when strongly heated, regenerates the element X.
Show the answer and explanation

Answer: E (Its oxide, when strongly heated, regenerates the element X.)

Explanation

X is potassium. Its oxide is very stable and does not break down to potassium on heating. The others are true: K2O takes up moisture to form deliquescent KOH, whose solution conducts, leaves white KOH on evaporation and reacts with aluminium giving hydrogen.