In this video, I perform tests for the presence of two gases, hydrogen and oxygen.
TEST FOR HYDROGEN:
Put a few milliliters of hydrochloric acid in a test tube. You can also use other acids, just as hydrobromic and hydroiodic acid. Nitric acid and sulfuric acid are not likely to liberate hydrogen when come in contact with a metal. Get a piece of magnesium (or zinc, iron, aluminum) and drop it in the test tube. Immediately cover the top with a wider test tube and let the reaction proceed.
Do NOT use sodium or potassium for this; they are potentially hazardous and the reaction can lead to an explosion. I ‘ll show how dangerous can this reaction be in the next video (with sodium). Here ‘s the link to that: https://www.youtube.com/watch?v=Idr9HbfJmuo
Now bring a match (or a lighter or even a candle) near the wide test tube, which is full of hydrogen gas, and you ‘ll notice a sharp, popping sound. This is hydrogen reacting with oxygen in the air to form water vapor. You can see it later condensing on the sides of the test tube.
TEST FOR OXYGEN:
Dissolve a few crystals of KMnO4 (potassium permanganate) in 100 mL of water. Pour slowly 100 mL of 3% hydrogen peroxide in the solution. You may also use more concentrated solution of hydrogen peroxide, but don’t exceed ~15-18% concentration. Oxygen is heavier than air, so it will stay at the bottom of the container.
When you finish with the hydrogen peroxide, you ‘re ready to test for oxygen. Light a match and bring it close to the container of oxygen. It will burn brighter, because the atmosphere in the container is pure oxygen. Be careful not to burn your fingers!
This demonstration can be done at school too.
Thanks for watching!
And feel free to ask me any question.
Post time: Jun-18-2017