Can Aeration Change the Equilibrium of Gases in Water?

In summary, the conversation discusses the effect of adding live plants to a vessel of water and diffusing atmospheric air into the water. It is stated that photosynthesis by the plants will increase the ratio of oxygen to carbon dioxide in the water, and that aerating the water will increase the level of CO2 dissolved in it. However, the final effect will depend on kinetics, and once equilibrium is reached, the composition of dissolved gases will remain the same. The presence of plants and animals will no longer matter in determining the composition of the dissolved gases.
  • #1
Subrosa
4
0
Hi, first time poster. Here's the scenario. In a given vessel containing a given amount of water at a given temp, gases from the air will reach equilibrium with those dissolved in the water contained in the vessel. Now suppose live plants are added to the water. During the day, photosynthesis will occur, which will skew the relative ratio of O2 and CO2 in the water towards the O2. If while this is occurring, atmospheric air is diffused into the water via an airstone powered by an air pump, what will be the effect on the ratio of CO2 to O2? It seems obvious to me that under these circumstances that aerating the water will increase the level of CO2 dissolved in it, however marginally. Is this correct? Thanks!
 
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  • #2
Yes, but the exact final effect will depends on kinetics - how fast gases are produced and how fast gases are exchanged.
 
  • #3
Thanks for the quick reply!
 
  • #4
Ok one more question. All else being equal, wouldn't increasing levels of aeration push the ratio more strongly back towards equilibrium (in this case higher CO2 levels)through increasing the surface area of the air/water interface?
 
  • #5
Once the speed of exchange is high enough, presence of plants/animals stops to matter, and the composition of dissolved gases is always the same (and in a simple equilibrium with those present in the atmosphere).
 
  • #6
My thoughts exactly sir. The water and air "want" to be at equilibrium with each other, and once equilibrium is reached no amount of air pumped through the water will change that equilibrium. Thank you again!
 

1. What is equilibrium of gases in water?

Equilibrium of gases in water refers to the state in which the amount of dissolved gas in water is balanced with the amount of gas present in the surrounding atmosphere. This is a dynamic process in which gas molecules are constantly moving between the water and air until a balance is reached.

2. How do gases dissolve in water?

Gases dissolve in water through a process called diffusion. This is when gas molecules move from an area of high concentration (the surrounding air) to an area of low concentration (the water). This continues until the concentration of gas in the water is equal to the concentration in the air.

3. What factors affect the equilibrium of gases in water?

The equilibrium of gases in water can be affected by several factors, including temperature, pressure, and the solubility of the gas in water. Higher temperatures and lower pressures generally result in less gas being dissolved in water, while higher solubility leads to more gas being dissolved.

4. What happens when the equilibrium of gases in water is disturbed?

If the equilibrium of gases in water is disturbed, the dissolved gas will either move back into the air or into the water until a new equilibrium is reached. For example, if the temperature of the water increases, more gas will be released into the air until the concentration of gas in the water is once again equal to the concentration in the air.

5. How is the equilibrium of gases in water important in aquatic ecosystems?

The equilibrium of gases in water is crucial for the survival of aquatic organisms. It affects the amount of oxygen and carbon dioxide available for aquatic plants and animals, and can also impact the pH level of the water. Changes in this equilibrium can be harmful to aquatic life and can disrupt the delicate balance of an ecosystem.

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