When the rate of evaporation equals the rate of condensation does the partial pressure of a volatile liquid in a sealed container change?
No, the partial pressure of a volatile liquid in a sealed container does not change when the rate of evaporation equals the rate of condensation. This is because the partial pressure of a gas is the pressure exerted by that gas in a mixture of gases. When the rate of evaporation equals the rate of condensation, the number of gas molecules in the mixture is constant, so the partial pressure of the gas is also constant.
The partial pressure of a gas can be calculated using the following equation:
P_A = n_A * R * T / V
where:
- P_A is the partial pressure of gas A
- n_A is the number of moles of gas A
- R is the universal gas constant
- T is the temperature in Kelvin
- V is the volume of the container
In a sealed container, the volume (V) and temperature (T) are constant. So, the partial pressure of the gas (P_A) is also constant, regardless of whether the rate of evaporation equals the rate of condensation.
This is why a cup of water left out in the open will eventually evaporate completely, even though the rate of evaporation slows down as the air becomes saturated with water vapor. The rate of condensation will eventually match the rate of evaporation, and the partial pressure of the water vapor will reach equilibrium.
I agree with Murtadha Shukur, that the partial pressure of a volatile liquid in a sealed container does not change when the rate of evaporation equals the rate of condensation. This is because the partial pressure of a gas is the pressure exerted by that gas in a mixture of gases. Dynamic equilibrium is important because it helps us understand how chemical reactions work. For example, when water evaporates from a glass, it eventually reaches dynamic equilibrium where the rate of evaporation equals the rate of condensation. This keeps the amount of water in the air constant. It reaches a stage where the rate of evaporation is equal to the rate of condensation. This phase is called the stage of equilibrium. As represented by the manometer, at this point the pressure exerted by the molecules is called the vapour pressure of the liquid. When the evaporation rate and condensation rate are equal, a state of saturation or equilibrium exists. If the air parcel is heated, the evaporation rate increases because the more energetic molecules can evaporate more easily. When the rate of condensation of the gas becomes equal to the rate of evaporation of the liquid or solid, the amount of gas, liquid and/or solid no longer changes. The gas in the container is in equilibrium with the liquid or solid. Condensation is the process by which water vapor in the air is changed into liquid water; it's the opposite of evaporation. Condensation is crucial to the water cycle because it is responsible for the formation of clouds. At any temperature, evaporation and condensation are actually occurring at the same time. Faster molecules from the liquid evaporate while slower molecules from the gas condense. Depending on the conditions, one process will happen at a faster rate than the other resulting in net evaporation or net condensation.
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