Methods of Collection
One way for gases to be collected is over water. But this can only be done with gases that are insoluble or only slightly soluble in water (else they would dissolve and you wouldn't collect them. For example: carbon dioxide, oxygen and hydrogen.
In this method a container is filled with water, a test tube is also partially filled with water and inverted and submerged in the water - it remains full. A pipe is put under the test tube, and as gas bubbles up into the test tube, it forces water from it; so that the gas is collected in the tube.
Another, more simple method is to displace air rather than water. If the gas has a density lower than that of air, it can be collected by upward delivery. But if, on the other hand, the gas has a density higher than air, it must be collected by downward delivery, or it would escape.
The next method of collection, the gas syringe, is not only for collection but also for measuring the volume of gas collected.
Put in a burning match
It will pop.
Put in a glowing match
It will reignite.
|Bubble gas through lime water (CaOH)
The water will turn cloudy
Bubble through orange potassium dichromate solution
Solution turns green.
Mix with ammonia gas
Forms dense white fumes.
Add damp red litmus paper
Paper turns blue.