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JAMB Chemistry 2002 Question 1

Question 1

Chemical Formulae and Equations

A compound contains 31.91% potassium, 28.93% chlorine and the rest oxygen. What is the chemical formula of the compound? [K = 39, Cl = 35.5, O = 16]

  1. A.KClO4
  2. B.KClO
  3. C.KClO2
  4. D.KClO3
Show the answer and explanation

Answer: D (KClO3)

Explanation

Oxygen = 100 − 31.91 − 28.93 = 39.16%. Moles: K 31.91/39 = 0.818, Cl 28.93/35.5 = 0.815, O 39.16/16 = 2.45, a ratio of 1 : 1 : 3, so KClO3.