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Questions and Answers
What is the most common oxidation state of selenium in its compounds?
What is the most common oxidation state of selenium in its compounds?
What is the main purpose of selenomethionine in the body?
What is the main purpose of selenomethionine in the body?
Which compound is formed by reacting elemental selenium with oxygen?
Which compound is formed by reacting elemental selenium with oxygen?
What is the primary reaction that produces selenous acid?
What is the primary reaction that produces selenous acid?
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Which selenium compound has been used as an antidandruff agent?
Which selenium compound has been used as an antidandruff agent?
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What is a significant characteristic of selenium trioxide compared to sulfur trioxide?
What is a significant characteristic of selenium trioxide compared to sulfur trioxide?
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What is the chemical composition of selenium disulfide?
What is the chemical composition of selenium disulfide?
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Which process leads to the production of selenium trioxide in the laboratory?
Which process leads to the production of selenium trioxide in the laboratory?
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Study Notes
Selenium Compounds: Properties and Applications
- Selenium (Se) compounds display various oxidation states, predominantly -2, +4, and +6.
- Naturally occurring selenium compounds include minerals like clausthalite, guanajuatite, tiemannite, and crookesite, often coexisting with sulfide minerals (e.g., pyrite, chalcopyrite).
- Essential for mammals, selenium-containing amino acids (selenomethionine and selenocysteine) are crucial components of selenoproteins.
- Selenocysteine exhibits lower reduction potential and pKa (5.47) compared to cysteine, contributing to antioxidant properties in certain proteins.
- Selenium compounds find diverse applications in semiconductors, glass/ceramic industries, medicine, metallurgy, etc.
Selenium Oxides
- Selenium forms two oxides: selenium dioxide (SeO2) and selenium trioxide (SeO3).
- Selenium dioxide (SeO2) is a polymeric solid in the solid state but exists as monomers in the gas phase.
- SeO2 dissolves in water to form selenous acid (H2SeO3). SeO2 is formed by reacting elemental selenium and oxygen.
- Selenous acid (H2SeO3) can also be synthesized by oxidizing elemental selenium with nitric acid.
- Selenium trioxide (SeO3) is thermodynamically unstable, decomposing above 185°C to selenium dioxide.
- Laboratory synthesis of SeO3 involves reacting anhydrous potassium selenate (K2SeO4) with sulfur trioxide (SO3).
Selenites and Selenium Disulfide
- Salts of selenous acid are known as selenites (e.g., silver selenite (Ag2SeO3), sodium selenite (Na2SeO3)).
- Hydrogen sulfide reacts with aqueous selenous acid producing selenium disulfide (SeS2).
- Selenium disulfide is composed of 8-membered rings with variable Se:S ratios (e.g., Se4S4, Se2S6).
- Selenium disulfide has applications as an antidandruff agent in shampoo, an inhibitor in polymer chemistry, a glass dye, and a reducing agent in fireworks.
Selenic Acid and Applications
- Selenic acid (H2SeO4) is produced by oxidizing selenium dioxide with hydrogen peroxide.
- Hot, concentrated selenic acid reacts with gold to form gold(III) selenate.
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Description
Explore the fascinating world of selenium compounds, their properties, and various applications. This quiz covers oxidation states, the significance of selenium in biology, and its use in industries such as semiconductors and medicine. Test your knowledge about selenium oxides and their behavior in different environments.
