Reaction of the breakdown of hydrogen peroxide and its features
Properties of hydroperite aka perhydrol
Hydrogen peroxide is an unstable substance. In pure form, it is unstable, and easily breaks down, with the process often being accompanied by an explosion. In water solutions, it is more stable, but oxygen is constantly released when the solutions are stored. This process accelerates from the effect of light, catalyzers or from heating. Catalysts can be compounds of iron, copper, manganese dioxide, cobalt, catalase enzymes and other substances
The chemical characteristics of hydrogen peroxide
Hydrogen peroxide is a transparent, colorless and slightly viscous liquid without taste or smell, which in large volumes has a bluish tinge. The substance is also known as hydroperite and perhydrol. It is 1.5 times heavier than water and can mix with it in any ratios. The molecular weight of hydrogen peroxide is 34.02, freezing point is 0.5 degrees Celsius, and boiling point is 67 degrees. The chemical formula is Н₂О₂.
Hydrogen peroxide is a non-combustible liquid that is fire- and explosion-hazardous, and a strong oxidizer which enters into reactions with many substances: hydrogen peroxide easily breaks down into oxygen and water when exposed to light, and also when it comes into contact with reducing and oxidizing substances, in interaction with an alkaline or on heating. In ideal conditions, Н₂О₂ breaks down slowly, with a speed of 1% per month. The speed of breakdown slows down in the cold, so the substance can be stored for a long time in a frozen state - from minus 0.5 degrees Celsius. In nature, Н₂О₂ is encountered in insignificant quantities – for example, in snow or rainwater.
The breakdown of hydrogen peroxide — the reaction in the laboratory
The catalytic breakdown of hydrogen peroxide in this experiment looks very effective. Take a conic flask with a capacity of 300 ml, and pour 15 ml of dishwashing liquid of any brand into it. In another flask, dissolve 4 grams of copper sulfate with plenty of strong ammonium solution – add the solution until the copper sulfate dissolves completely. Blue copper ammine forms in the reaction.
Pour the copper ammine solution into the flask with the dishwashing liquid and mix thoroughly. Then place the flask on a table and quickly add 70 ml of a 30-50% solution of hydrogen peroxide. A large amount of gas is released, and a fountain of foam spurts from the flask. The entire work space is covered with large clumps of foam. As the reaction of breakdown of hydrogen peroxide takes place with release of heat, steam rises from the foam.
30-50% hydrogen peroxide can be replaced with hydrogen peroxide solution that is sold in pharmacies. To make sure that the breakdown of hydrogen peroxide takes place quickly, we recommend that you use a high concentration of H₂O₂. On the other hand, the catalyst of the breakdown of H₂O₂ should be quite active — you can use copper ammine or potassium permanganate. Sometimes potassium iodide is used, but experiments with this substance are not always successful.
Studying the reaction of the breakdown of hydrogen peroxide
Liquid hydrogen peroxide has greater energy than liquid water and gaseous oxygen by 23 kcal, i.e. it breaks down exothermically. Liquid Н₂О₂ releases 13 kcal in the reaction of the breakdown into oxygen and water vapor. Using simple arithmetic, we can easily calculate that when one cubic centimeter of pure liquid hydrogen peroxide breaks down into oxygen and water, self-heating takes place so that all the water moves to a vaporous state, and the resulting mixture of gaseous oxygen and water molecules reaches a temperature of around 1000 degrees Celsius.
As a result of the increase in temperature, the gases expand, and 1 cm of liquid hydrogen peroxide gives 7000 cm of hot gases when it breaks down. As the breakdown takes place instantaneously with an expansion of 7000 times, there is a very dangerous explosion. As soon as a small amount of this hydrogen peroxide breaks down, the substances released in the breakdown heat the neighboring particles of hydrogen peroxide, which in their turn break down from heating, release more heat, and so on. The reaction that starts in one point or small drop of hydrogen peroxide immediately spreads throughout the entire mass of the substance, and an explosion takes place, and in the presence of combustible substances, there is a flash.
For example, even a 60% solution of hydrogen peroxide at room temperature ignites wood chips and paper on contact with them. The lower the concentration of hydrogen peroxide, the less dangerous it is, as the heat from the chemical reaction of the breakdown goes towards the evaporation of a large mass of water, which has considerable thermal capacity and heat of evaporation. It is clear that a 10% solution of hydrogen peroxide can heat itself up to boiling temperature on breaking down, and even a 3% solution of hydrogen peroxide down can heat itself up 20 degrees above its initial temperature when it breaks down.
If concentrated hydrogen peroxide is severely contaminated, the breakdown reaction may accelerate, because of the self-heating of the substance. This process, which is slow at first, may reach an extreme speed, accompanied by the explosion of the container, despite the presence of a vent. Possible accidents can be prevented by constantly raising the temperature of the product over a certain period of time. The speed of the increase in temperature is the function of the degree of contamination. If the heating is not stopped, the contaminated hydrogen peroxide should be quickly diluted with water and poured away. Large reservoirs for storing concentrated hydrogen peroxide should be equipped with thermometers, in order to provide warnings of a possible breakdown.