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JAMB Physics 1981 Question 2

Question 2

Change of State and Vapours

A vapour is said to be saturated when

  1. A.more molecules return to the liquid than leave it
  2. B.a dynamic equilibrium exists between the liquid molecules and the vapour molecules at a given temperature
  3. C.the vapour pressure is atmospheric
  4. D.the temparature of the vapour varies
  5. E.all molecules are moving with the same speed.
Show the answer and explanation

Answer: B (a dynamic equilibrium exists between the liquid molecules and the vapour molecules at a given temperature)

Explanation

A saturated vapour is one in dynamic equilibrium with its liquid: molecules leave and return at the same rate.