Gases are collected using different apparatus according to their properties. Do you know what those methods are? In this lesson, we will be learning about those methods.
Displacement of Water
Downward Delivery
Upward Delivery
The physical properties which affect their way of collection are solubility (in water) and density (compared to air).
Displacement of water is suitable for collecting the gases which are insoluble in water because water is used to collect them. Those gases are carbon dioxide, hydrogen and oxygen.
Downward delivery method is used to collect the gases which are denser than air and soluble in water. Such gases are chlorine, hydrogen chloride and sulfur dioxide. The gas is delivered towards down as it is denser than air. Gas jar is placed in a position where the gas enters from the top through the delivery tube. Density of air is 30: gases more dense than air have density which is more than 30 and less dense have density is less than 30.
Upward delivery method is just the opposite of downward delivery. In this gases are less denser than air and are soluble in water such as ammonia. Gas jar is placed upside down so the gas enters from the bottom through the delivery tube.
We need to collect gases in order to know more about the reactions that have occurred or we use the collected gases in other reactions. Some reactions require the use of dry gases.
To dry gases we pass them through drying agents. The methods used are:
Concentrated Sulfuric Acid
Quicklime ( calcium oxide )
Fused calcium chloride
Concentrated Sulfuric Acid:
It is used to dry most gases, including chlorine and hydrogen chloride.
Quicklime ( calcium oxide ):
It is used to dry ammonia.
Fused Calcium Chloride:
It is calcium chloride that has been heated to remove all traces of water. It can be used to dry most gases.
*All pictures are from google*
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