In most reactions, gases are released. Most common of these gases are:
Hydrogen gas
Carbon dioxide gas
Reactions like:
Sulfur + Hydrochloric acid -------- sulfur chloride + hydrogen
Copper Carbonate + Hydrochloric acid --------- copper chloride + water + carbon dioxide
Now, how do you test for these gases?
Hydrogen Gas:
Hydrogen gas, formed in a reaction is collected in a test tube. Place a burning matchstick, on the top of the test tube containing hydrogen gas. If the flame goes off with a "pop" sound, it means hydrogen gas is present.
Carbon dioxide Gas:
Carbon dioxide gas, released in a reaction is collected in a test tube. Now there are 2 methods to test for hydrogen gas.
Litmus Paper: When blue litmus is placed in the test tube containing carbon dioxide, if the blue litmus paper turns to red, it means carbon dioxide gas is present.
Limewater: When limewater (calcium carbonate) is poured into the test tube, if the limewater turns to a milky, chalky color, it means carbon dioxide gas is present.
These collected gases are useful, by identifying these gases we can know more about the reactions occurred and sometimes these gases can be used in other reactions as well.
*All pictures are taken from google*
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