Which one of the following is a commonly used to quench excess oxidizing agent?
A) sodium thiosulfate
B) sodium sulfate
C) sodium chloride
D) magnesium sulfate
The correct answer and explanation is:
The correct answer is A) sodium thiosulfate.
Sodium thiosulfate is commonly used to quench or neutralize excess oxidizing agents, especially in situations where strong oxidizers like iodine or chlorine are involved. It works by reducing these oxidizing agents into less harmful substances. For example, when sodium thiosulfate is added to iodine (I₂), it reacts to form iodide ions (I⁻) and tetrathionate ions (S₄O₆²⁻), effectively neutralizing the iodine.
The chemical reaction for iodine neutralization is as follows: I2+2Na2S2O3→2NaI+Na2S4O6I_2 + 2Na_2S_2O_3 → 2NaI + Na_2S_4O_6
This reduction process is important because oxidizing agents can be harmful or even dangerous if left unchecked. In laboratory settings, sodium thiosulfate is used frequently in titrations, particularly in redox titrations involving iodine. It’s also used in photographic processing and in treating some types of poisonings, such as cyanide poisoning, where it helps neutralize the toxic substances by reduction.
Other chemicals listed, like sodium sulfate, sodium chloride, and magnesium sulfate, do not typically serve as quenching agents for oxidizers. While they may have other applications, they do not possess the same reducing properties as sodium thiosulfate. Sodium sulfate is mainly used as a drying agent, sodium chloride is common in various reactions but not for quenching oxidizers, and magnesium sulfate is used primarily as a desiccant or in medical treatments.
Therefore, sodium thiosulfate is specifically chosen for its ability to effectively neutralize excess oxidizing agents in a variety of settings.