Methods for obtaining oxygen
How to obtain O₂ at home or in the lab
Oxygen is a gas without taste, smell or color. It is the second most common gas on the planet after hydrogen. It is a strong oxidizing agent and a chemically active non-metal. This gas was discovered by several scientists at the same time in the 18th century, and the first scientist to obtain oxygen was the Swedish chemist Scheele in 1772. The French chemist Lavoisier conducted research into the element, and gave it the name of "oxygène". You can detect oxygen with a smoldering piece of wood, which flares up brightly on contact with the gas.
The importance of oxygen
This gas participates in combustion processes, and oxygen is processed by green plants, which carry out the process of photosynthesis with their leaves, enriching the atmosphere with gas that is vital for life.
How can we obtain oxygen? The gas is obtained from the air by industrial methods, in which the air is purified and compressed. Our planet has enormous supplies of water, the chemical composition of which partially consists of oxygen. This means that the gas can be obtained by breaking down water. We can do this at home.
How to obtain oxygen from water
The following tools and materials are required for the experiment
• electricity source;
• 2 plastic cups;
• 2 electrodes;
• Galvanic bath.
Let’s examine the process. Pour water into a galvanic bath until it is over half full, and add 2 ml of caustic nitrate or diluted sulfuric acid – this increases the electrical conductivity of the water. Make holes at the bottom of the plastic cups, and pull electrodes through the holes – carbon plates. We must isolate the air layer between the cup and the plate. We place the cups in the bath so that the electrodes are in the water, and the cups are upside down. Between the water surface and the bottom of the cup, there should be a minimum of air.
We solder a metal wire to each electrode, and connect them to the electricity source. The electrode connected to the negative pole is called the cathode, and the one connected to the positive pole is the anode.
An electric current passes through the water – electrolysis of the water is carried out.
A chemical reaction takes place, forming two gases. Hydrogen collects in the cup with the cathode, and oxygen in the cup with the anode. We determine that gas has formed in the cups with the electrodes by the bubbles of air that rise out of the water. Through a pipe we draw the oxygen out of the cup into another container.
The chemical experiment to extract oxygen from water should only be carried out observing safety rules. The gases obtained in the process of water electrolysis must be mixed. The hydrogen obtained should not come into contact with the air because of its explosive nature. For safe and interesting experiments with different gases click here.
How to obtain oxygen by the laboratory method
First method: pour calcium permanganate into a test tube, and put the test tube over a burner. The manganese crystal heat up, and oxygen is released. We catch the gas with a gas bath. Result: 10 g of calcium permanganate releases 1 l of oxygen.
Second method: we pour 5 g of nitrate into a test tube, and seal the test tube with a fire-resistant cork with a glass pipe in it. We hold the test tube in place on a stand, and place a bath with sand under it, to avoid excessive heating. We turn on the gas burner and direct the flame at the test tube. The substance melts, and oxygen is released. We collect the gas through the glass tube in a balloon placed over it.
Third method: we pour potassium chlorate into a test tube and place the test tube on a gas burner, after sealing it with a fire-proof cork with a glass tube in it. The potassium chlorate releases oxygen in the process of heating. We collect the gas through the pipe in a balloon placed over it.
Fourth method: we hold a test tube in place with a stand, and pour hydrogen peroxide into the test tube – the unstable compound breaks down into oxygen and water on contact with air. To accelerate the reaction of the release of oxygen, we add active charcoal to the test tube. We seal the test tube with a fireproof cork with a glass pipe in it, place a balloon over the pipe and collect the oxygen.
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