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How Solubility affects collection of gases by
Physical Property: Solubility
Solubility is the degree to which a substance (solute) can dissolve in a solvent to form a solution (Refer here for more information)
Explaining the Set-Up
Displacement of water as a gas collection method can be done using a
test-tube (for small volumes) or gas jar (for large volumes). These apparatus are inverted, where the gases are delivered upwards over water
The reason for this is because gas are less dense as compared to water.
Reason: The particles of gases are more spaced apart as compared to particles of liquid water (closely packed)
How does solubility of gases in water affect whether displacement of water can be used?
For the displacement of water experiment, whether a gas can be collected depends on its solubility in water (solvent)
If a gas is soluble in water, displacement of water cannot be used as the gas will dissolve in water and is unable to be collected.
Example: Ammonia
If a gas is insoluble or slightly soluble in water, displacement of water can be used
Example (insoluble in water): Hydrogen, Oxygen
Example (slightly soluble in water): Carbon Dioxide
Examples of gases that are soluble or insoluble in water
Oxygen is insoluble in water
It is often used to aerate fish tanks, where bubbles are observed.
Carbon dioxide is slightly soluble in water
Carbon dioxide can be found in carbonated drinks like coke. These drinks are slightly acidic as some carbon dioxide has dissolved in water, but gas bubbles can still be observed
Ammonia is soluble in water
Ammonia can often be found as a solution
Can displacement over water be used? YES
Can displacement over water be used? YES
Can displacement over water be used? NO
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