Question

e choice: write the letter of the correct choice in the blank.

1. which of the following statements best describes what is meant when a liquid and its vapor are said to be in equilibrium?

a. the mass of vapor and the mass of liquid are equal.
b. the liquid and its vapor are in a closed container.
c. increasing temperature will increase the amount of vapor.
d. the rates of evaporation and condensation are equal.

1. what is the concentration of a solution containing 2.4 mol of nacl dissolved in 3.0 l of water?

a. 0.80 m
c. 3.0 m
b. 2.4 m
d. 7.2 m

1. a chemist wishes to prepare 1.0 l of 0.10 m h₂so₄ by diluting concentrated (18 m) h₂so₄; how much concentrated h₂so₄ is required?

a. 3.0 ml
c. 9.0 ml
b. 6.0 ml
d. 12 ml

1. what is the concentration of a solution containing 0.1 mol of kmno₄ dissolve in 500. g of water?

a. 0.0002 m
c. 0.02 m
b. 0.002 m
d. 0.2 m
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Explanation:

Step1: Recall the concept of equilibrium in physical chemistry

In a liquid - vapor equilibrium, it is a dynamic equilibrium. The forward process (evaporation) and the reverse process (condensation) occur at the same rate.

Step2: Analyze each option

• Option a: The mass of vapor and liquid being equal is not the definition of equilibrium. For example, if you have a large amount of liquid and a small amount of vapor in a closed container, they can still reach equilibrium without having equal masses.
• Option b: Just being in a closed container is a necessary condition for equilibrium to be established (to prevent the vapor from escaping), but it does not define the equilibrium state.
• Option c: Increasing temperature generally increases the amount of vapor (by increasing the evaporation rate more than the condensation rate initially until a new equilibrium is reached), but this is a property of the system when temperature changes, not the definition of equilibrium.
• Option d: When the rates of evaporation and condensation are equal, the system is in a state of dynamic equilibrium. The amount of liquid and vapor remains constant over time (macroscopically), although at the microscopic level, molecules are constantly moving between the liquid and vapor phases.

Answer:

d. The rates of evaporation and condensation are equal.