Which test can identify carbon dioxide gas?

The test that can effectively identify carbon dioxide gas is to bubble it through limewater. When carbon dioxide is bubbled through limewater, which is a dilute solution of calcium hydroxide, a chemical reaction occurs. This reaction produces calcium carbonate, causing the limewater to turn milky or cloudy. The formation of this milkiness indicates the presence of carbon dioxide in the gas sample.

This method is reliable and specific for detecting carbon dioxide, as the reaction produces a distinct visual change that can easily be observed. Other tests, such as burning a splint or bubbling the gas through water, do not provide a definitive indication of carbon dioxide specifically and may not yield any observable or distinguishing results. Observing gas escaping from a reaction does not provide specific information about the gas's identity without further testing.