Why is carbon dioxide gas collected in an erect gas jar?

An erect gas jar is used because it is easier to put inlets/outlets in one end rather than on a side or on the bottom which is needed to place it on a stable surface. read more

Carbon dioxide gas is denser than regular air at normal air pressure. This means that if you collect it in an upright container, it will not ‘mix’ with the regular air unless it is disturbed. But, it doesn’t HAVE to be collected that way. read more

Collecting gases over water. Sometimes gases are collected over water. The gas produced in a reaction is bubbled through a trough of water and into an upturned gas jar filled with water. The bubbles of gas collect in the top of the gas jar and push the water out of the bottom. If enough gas is produced it completely replaces the water in the gas jar. read more