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JAMB Chemistry 2011 Question 35

Question 35

Hydrogen, Oxygen and Oxides

In the laboratory preparation of oxygen, dried oxygen is usually collected over

  1. A.hydrochloric acid
  2. B.mercury
  3. C.calcium chloride
  4. D.tetraoxosulphate (VI) acid
Show the answer and explanation

Answer: B (mercury)

Explanation

Collecting over water would make the gas wet again, so dry oxygen is collected over mercury (it is dried with conc. H2SO4 first).