Question

1.

a）Why do you think pure or very concentrated solutions of hydrogen peroxide are considered to be dangerous?  

b) Why must metal containers never be used for the storage of hydrogen peroxide?

c) Why does blood cause hydrogen peroxide to decompose? Also, describe why using hydrogen peroxide is a good protector against certain bacteria.

d) Hydrogen peroxide decomposes to water and oxygen gas. Write out the equation, describing what is oxidized and what is reduced, and what material is the oxidizing agent and what material is the reducing agent.

Answer 1

a) Concentrated hydrogen peroxide is a dangerously reactive substance, because its decomposition to form water and oxygen is highly exothermic. The following thermochemical reaction demonstrates that fact:

     

It is a powerful oxidizing agent that can cause spontaneous combustion when it comes in contact with organic matter or some metals, such as copper, silver or bronze.

At high concentrations it is corrosive; its contact causes whitening of the skin as a subsequent itching, due to the formation of small blisters with oxygen inside the skin which can generate a subcutaneous efisema. The peroxide to have contact with the eyes even in concentrations as low as 5% can cause permanent damage to the cornea and possibly blindness.

b) Hydrogen peroxide is denser than water but is miscible in water in all proportions. It is a non-combustible liquid, but if the hydrogen peroxide is placed in a metal container it can interact in the medium with the metals in the container since it is a very oxidizing agent and the heat and oxygen during the decomposition can ignite the materials that are in the material of the container. It is therefore appropriate that the storage of this reagent is in a closed plastic container and that all contact surfaces are not non-porous.

c) The blood contains an enzyme that is catalase, which breaks it down quickly, producing the oxygen that is responsible for cleaning the sting and the bubbles we observe. Since many of the pathogenic bacteria are anaerobic (they can not live with oxygen), they die in the oxygen-rich white foam that is produced when the blood of the wound acts on the oxygenated water.

However, the most important function of these enzymes is inside the body. The peroxide ions and their superperoxides that are produced as a byproduct of metabolism are undesirable because of the oxidants and reagents that are, generating free radicals and therefore causing serious damage to cells. It is the enzymes catalases, peroxidases and superoxide dismutases that exist within our body that specifically increase the rate of decomposition of these toxic substances.

Like the ozone layer, hydrogen peroxide kills pathogens by oxidation, and this is the safest disinfectant on the market. Hydrogen peroxide is a general antiseptic, its mechanism of action is due to its oxidizing effects that produce OH and free radicals that attack a wide variety of organic compounds, including lipids and proteins that make up the cell membranes of microorganisms.

d)   

general reaction

  

Hydrogen peroxide is able to act either as an oxidizing agent or as a reducing agent. The equations that were shown present the half-reactions in acid medium