The question asks about substances that can be used to prevent the decomposition of hydrogen peroxide (H_2O_2). Let's go through the given options to understand which compound acts as a stabilizer for H_2O_2:
Urea: Urea is known to stabilize hydrogen peroxide by forming a complex. This complex reduces the rate at which hydrogen peroxide decomposes into water and oxygen. Therefore, urea is commonly used as a stabilizer for H_2O_2.
Formaldehyde: Formaldehyde is not known to act as a stabilizer for hydrogen peroxide. In fact, formaldehyde can undergo reactions in the presence of hydrogen peroxide that do not help in the stabilization process.
Formic acid: Formic acid doesn't prevent the decomposition of hydrogen peroxide and might even promote it. Therefore, it is not a suitable choice for stabilization.
Ethanol: Ethanol does not stabilize hydrogen peroxide. It can react with hydrogen peroxide but does not prevent its decomposition.
Based on the evaluation of each option, the correct answer is Urea, as it effectively prevents the decomposition of H_2O_2 by stabilizing it.
