Why does laboratory made oxygen stuff a ball of cotton at the mouth of the test tube

with potassium permanganate.

When producing oxygen, a ball of cotton should be placed at the mouth of the test tube first, and the reason is: to prevent potassium permanganate powder from entering the water tank with the gas flow when heated; When producing oxygen in the laboratory, if the drainage method is used.

When collecting gas, it can be collected when the bubbles are released continuously and evenly When the reaction is stopped, if the alcohol lamp is extinguished first.

The catheter is then withdrawn from the sink, and the result is that the water is sucked into the test tube, causing the test tube to burst

1) Oxygen has combustible properties, which can rekindle wooden strips with sparks, if the upward air exhaust method is used.

When collecting, the way to prove that the oxygen in the bottle is full is to place the spark strip into the mouth of the cylinder, and if the strip is rekindled, it proves that the oxygen has been collected

2) Stick the Martian wood into the bottle, if it rekindles, the colorless gas in the bottle is oxygen

Therefore, the answer is: to prevent potassium permanganate powder from entering the sink with the gas flow when heated; continuous uniformity; The water is sucked into the test tube, causing the test tube to burst;

1) Place the wooden strip with sparks at the mouth of the gas collection cylinder, if the wooden strip rekindles, it proves that the oxygen has been collected

2) Stick the Martian wood into the bottle, if it rekindles, the colorless gas in the bottle is oxygen

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