NECO 2001 Physics · Question 9

Which statements(s) is/are NOT true? I. A saturated vapour is one that is in equilibrium with its liquid in a…

Question

Which statements(s) is/are NOT true? I. A saturated vapour is one that is in equilibrium with its liquid in a closed space. II. A vapour contains molecules with varying kinetic energy and their distances apart are smaller than those of the molecules of a liquid III. Relative Humidity = $\frac{\text{Saturated vapour pressure at dew point}} {\text{Saturated vapour pressure at air temperature}}$ x 100% IV. The saturated vapour pressure of water increases with temperature

A.I only
B.II only
C.II and III only
D.III and IV only
E.II, III and IV only

Answer: B. II only

Explanation written with AI and checked against the answer key

Analyzing each statement I. A saturated vapour is one that is in equilibrium with its liquid in a closed space. This is true. Saturated vapour is in dynamic equilibrium with its liquid, so the rate of evaporation equals the rate of condensation. II. A vapour contains molecules with varying kinetic energy and their distances apart are smaller than those of the molecules of a liquid. This is false. The molecules in a vapour (gas phase) are much farther apart than those in a liquid. The first part, that the kinetic energies vary, is true, but the claim about distances is wrong. III. Relative Humidity = (SVP at dew point ÷ SVP at air temperature) × 100% This is true. Relative humidity is the ratio of the actual vapour pressure to the saturated vapour pressure at the air temperature. The actual vapour pressure of the air equals the SVP at the dew point, because the air becomes saturated when cooled to the dew point. IV. The saturated vapour pressure of water increases with temperature. This is true. A higher temperature gives more molecules enough energy to escape, so the SVP rises. Conclusion Only statement II is NOT true. Answer: B (II only) Exam tip: In "which is NOT true" questions, test each statement separately. Remember that vapour and gas molecules are far apart, while liquid molecules are close together. For relative humidity, think "SVP at dew point over SVP at air temperature."

AI can make mistakes. Report anything that looks wrong.