Does Hydrogen Peroxide Expire?
Yes, hydrogen peroxide does expire, and using expired hydrogen peroxide can be ineffective.
Stabilised hydrogen peroxide refers to a solution of hydrogen peroxide that contains additives that slow down decomposition. Despite this, stabilised hydrogen peroxide will also expire.
As an oxidising biocide, hydrogen peroxide breaks down into water and oxygen at a rate that is dependent on a number of factors. It is important to check the expiration date on the packaging before using hydrogen peroxide or stabilised hydrogen peroxide.
Shelf Life Of Stabilised Hydrogen Peroxide
Not all stabilised peroxide products are equal, EndoSan Stabilised Hydrogen Peroxide is manufactured with a shelf life of three years meaning it will remain stable and effective for the full duration of this time (provided it is stored correctly in the container and in line with the directions on the label).
When dosed into water EndoSan will also remain stable for weeks at both cold and hot temperatures (depending on the bacterial load and quality of the water). Regular hydrogen peroxide will only remain stable for a number of hours.
Why Does Hydrogen Peroxide Decompose?
Hydrogen peroxide is a relatively unstable compound due to the presence of an oxygen-oxygen bond, which is weaker compared to other chemical bonds. This weak bond makes hydrogen peroxide prone to decomposition, the shelf life and longevity of hydrogen peroxide can be affected by several factors, including:
Concentration
Higher concentrations of hydrogen peroxide tend to expire faster because they are more unstable than lower concentrations. The decomposition process of hydrogen peroxide occurs when its molecules break down into water and oxygen. The higher the concentration of hydrogen peroxide, the more unstable the molecules are, and the more likely they will break down into water and oxygen. This is not the case with EndoSan Stabilised Hydrogen Peroxide due to the advanced stabilisation of the product.
Temperature
Temperature can play a significant role in the expiration of hydrogen peroxide. Higher temperatures can accelerate the decomposition process of hydrogen peroxide, causing it to expire more quickly.
This is because high temperatures cause the molecules of hydrogen peroxide to vibrate more vigorously, which can cause them to break down into water and oxygen more rapidly. As a result, hydrogen peroxide is best stored in cool, dark places away from any heat sources, such as radiators, ovens, or bright sunlight.
On the other hand, lower temperatures can help to slow down the decomposition process, which can prolong the shelf life of hydrogen peroxide. However, it is important to store hydrogen peroxide at temperatures above freezing point since freezing can damage the container or affect the potency of the solution. The ideal storage temperature for hydrogen peroxide is typically between 2°C to 18°C (35°F to 65°F).
Exposure to light
Ultraviolet (UV) light, in particular, can cause hydrogen peroxide to break down into water and oxygen more quickly than it would in the absence of light. This is because UV light energy can excite the molecules of hydrogen peroxide, making the bonds between them more unstable and prone to breakage.
As a result, it is best to store hydrogen peroxide in opaque containers that protect it from light, especially direct sunlight. Transparent or translucent containers can allow light to penetrate into the solution, which can accelerate the decomposition process of hydrogen peroxide, causing it to expire sooner.
Contamination
Contamination with foreign substances, such as dirt or organic matter, can accelerate the decomposition process. When hydrogen peroxide is contaminated, it can react with the contaminant and accelerate the decomposition process, causing it to expire more quickly. This is because the contaminants can act as catalyzers, which can speed up the reactions of decomposition.
Contamination can occur when hydrogen peroxide comes into contact with organic or inorganic materials, such as dirt, dust, rust, or metal ions. In addition, contamination can also occur through improper storage or handling of the solution.To avoid contamination, it is advisable to store hydrogen peroxide in clean, dry containers that are free of any debris or residues. Also, be sure to use clean tools when handling hydrogen peroxide and avoid exposing it to materials that may react with it.
Natural Decomposition of Hydrogen Peroxide
In the absence of a catalyst, hydrogen peroxide decomposes naturally and slowly over time. This process is known as spontaneous decomposition. When hydrogen peroxide breaks down, it forms water (H2O) and oxygen gas (O2) as by-products. The reaction can be represented by the following equation:
H2O2 -> H2O + O2
The natural decomposition is accelerated when exposed to the catalysts mentioned above, which provide the energy necessary to break the oxygen-oxygen bond.
What Catalyst is Used in the Decomposition of Hydrogen Peroxide?
In the laboratory, the most common catalyst used for the decomposition of hydrogen peroxide is a substance called manganese dioxide (MnO2). Manganese dioxide is a black, powdery compound, and it acts as a surface catalyst, meaning it provides a suitable surface for the hydrogen peroxide molecules to interact with.
Why do Catalysts Speed Up Reactions?
Catalysts are substances that enhance the rate of a chemical reaction without undergoing any permanent change themselves. They achieve this by providing an alternative reaction pathway with a lower activation energy. In simpler terms, catalysts make it easier for the reactant molecules to collide and react, thus speeding up the overall process.
How Does Hydrogen Peroxide Decompose in Chemical Reactions?
The decomposition of hydrogen peroxide in the presence of a catalyst follows a different reaction pathway compared to natural decomposition. The manganese dioxide catalyst provides sites where hydrogen peroxide molecules can interact and react, without being consumed in the process.
The manganese dioxide catalyst acts as a surface onto which the hydrogen peroxide molecules can adsorb, forming bonds with the manganese atoms. This weakens the oxygen-oxygen bond within the hydrogen peroxide, making it more susceptible to breaking.
Once the bond is weakened, the reaction proceeds as follows:
- The weakened oxygen-oxygen bond breaks, forming hydroxyl radicals (OH•).
- These highly reactive hydroxyl radicals react with other hydrogen peroxide molecules, breaking their bonds as well.
- This chain reaction continues until most of the hydrogen peroxide has decomposed, resulting in the formation of water and oxygen gas.
The presence of the catalyst allows the decomposition reaction to occur at a faster rate compared to natural decomposition, enabling efficient use of hydrogen peroxide in various applications.
