Like sugar or salt, gases can also dissolve in water. Numerous variables affect how much dissolves. Think about a carbonated drink. The carbon dioxide gas has dissolved into the liquid, causing it to fizz.
Factors affecting gas solubility:
- Temperature:
- More dissolved gas can be held in colder water than in warmer water.
- Consider how quickly heated soda becomes flat compared to cold drink.
- Pressure:
- More gas dissolves under higher pressure.
- To maintain their sparkle, carbonated drinks are bottled under pressure for this reason.
- Type of gas:
- Certain gases are more soluble in water than others.
- For instance, compared to oxygen, carbon dioxide is more soluble.
How it works:
- The molecules in gas are always moving.
- As soon as they make touch with water. Some of them dissolve after becoming caught in the spaces between the molecules of water.
- What is the number of gas molecules dissolved in water? The ratio of people getting into the water to those getting out and back into the air determines this.
The primary formula governing the solubility of gases in water is Henry’s Law:
C = kH * P
Where:
- C is the concentration of the dissolved gas. In the liquid (usually in moles per liter).
- kH is the Henry’s law constant. Which is specific to each gas and varies with temperature.
- P is the partial pressure of the gas above the liquid.
Interpretation:
- Henry’s Law states that the concentration of a gas dissolved in a liquid is directly proportional to the partial pressure of the gas above the liquid. In simpler terms, the higher the pressure of the gas above the water, the more of that gas will dissolve in the water.
- The Henry’s law constant (kH) acts as a proportionality factor. It determines how much of a particular gas will dissolve at a given pressure and temperature. It’s important to note that kH values are specific to each gas and vary with temperature.
Additional Considerations:
- Temperature Dependence: The solubility of most gases in water decreases as the temperature increases.
- Non-ideal Behavior: Henry’s Law is most accurate for dilute solutions and gases. Which do not react chemically with water. For gases that react with water (e.g., ammonia, carbondioxide), the relationship between concentration and pressure is more complex.
- Salinity: The presence of salts in water can also affect gas solubility.
Why it is required:
- Aquatic life: Fish and other underwater creatures need dissolved oxygen to breathe.
- Carbon cycle: The ocean absorbs a lot of CO2 from the atmosphere, helping to regulate the climate.
- Industry: Many industrial processes involve dissolving gases in water, like in the production of fertilizers.
Examples:
- Fish tank: An air pump adds oxygen to the water to keep fish alive.
- Soda: The fizz is carbon dioxide gas dissolved under pressure.
- Deep-sea diving: Divers need to be careful of nitrogen dissolving in their blood at high pressure, which can cause decompression sickness.
Further Reading : https://byjus.com/chemistry/henrys-law/
