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Sunday, 16 August 2026
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Physics Past Questions and Answers

Topic: Vapours

Jamb Physics Questions - Vapours

Question 6:
Which of the following conditions will make water boil at a temperature of 100oC when the atmospheric pressure is 750mmHg?
  • A Increase the external pressure
  • B Reduce the external pressure
  • C Heat more rapidly at the same pressure
  • D Reduce the external pressure by a quarter
View Answer & Explanation
Question 7:
The saturated vapour pressure of a liquid increases as the
  • A Volume of the liquid increases
  • B Volume of the liquid decreases
  • C Temperature of the liquid increases
  • D Temperature of the liquid decreases
View Answer & Explanation
Question 8:
If a room is saturated with water vapour, the temperature of the room must be
  • A At 0<sup style='font-size: smaller;'>o</sup>C
  • B Above the dew point
  • C At 100<sup style='font-size: smaller;'>o</sup>C
  • D Below or at the dew point
View Answer & Explanation
Question 9:
A vapour is said to be saturated when
  • A More molecules return to the liquid than the amount that left it
  • B A dynamic equilibrium exists between the molecules of the liquid and the vapour molecules at a given temperature
  • C The vapour pressure is equal to the atmospheric pressure
  • D All molecules are moving with the same speed in all directions at a given temperature
View Answer & Explanation
Question 10:
I. A liquid boils when its saturated vapour pressure is equal to the external pressure
II. Dissolved substances in pure water lead to increase in the boiling point.
III. When the external pressure is increased, the boiling point increases.
IV. Dissolved substances in pure water decrease the boiling point.
Which combination of the above are peculiarities of the boiling point of a liquid?
  • A I, II and III
  • B I, II, III and IV
  • C I, II and IV
  • D II, III and IV
View Answer & Explanation