What are the alternative names listed for Triuranium octoxide?

The alternative names provided for Triuranium octoxide are Uranium(V,VI) oxide, Pitchblende, and C.I. 77919.

What is the CAS Registry Number for Triuranium octoxide?

The CAS Registry Number for Triuranium octoxide is 1344-59-8.

What is the chemical formula for Triuranium octoxide?

The chemical formula for Triuranium octoxide is U₃O₈.

What is the molar mass of Triuranium octoxide?

The molar mass of Triuranium octoxide is 842.08 g/mol.

What is the density of Triuranium octoxide?

The density of Triuranium octoxide is 8.38 g/cm³.

At what temperature does Triuranium octoxide melt?

Triuranium octoxide melts at 1,150 °C (2,100 °F; 1,420 K).

What happens to Triuranium octoxide at 1,300 °C?

At 1,300 °C (2,370 °F; 1,570 K), Triuranium octoxide decomposes to uranium dioxide (UO₂).

Is Triuranium octoxide soluble in water?

No, Triuranium octoxide is insoluble in water. This means it does not dissolve when mixed with water.

In which common acids is Triuranium octoxide soluble?

Triuranium octoxide is soluble in nitric acid and sulfuric acid.

What is the standard molar entropy of Triuranium octoxide?

The standard molar entropy (S°₂₉₈) of Triuranium octoxide is 282 J·mol⁻¹·K⁻¹.

What is the standard enthalpy of formation for Triuranium octoxide?

The standard enthalpy of formation (ΔfH°₂₉₈) for Triuranium octoxide is -3575 kJ·mol⁻¹.

What GHS pictograms are associated with Triuranium octoxide?

The GHS pictograms associated with Triuranium octoxide include the skull and crossbones (indicating toxicity), the silhouette (indicating a health hazard), and the dead tree/fish (indicating an environmental hazard).

What is the signal word used for GHS labelling of Triuranium octoxide?

The signal word for GHS labelling of Triuranium octoxide is Danger.

What are the GHS hazard statements for Triuranium octoxide?

The GHS hazard statements for Triuranium octoxide are H300 (Fatal if swallowed), H330 (Fatal if inhaled), H373 (May cause damage to organs through prolonged or repeated exposure), and H411 (Toxic to aquatic life with long lasting effects).

What is Triuranium octoxide (U₃O₈) generally described as in terms of appearance and odor?

Triuranium octoxide (U₃O₈) is described as an olive green to black, odorless solid.

How is Triuranium octoxide commonly encountered in the context of uranium processing?

Triuranium octoxide is one of the more popular forms of yellowcake, which is an intermediate step in uranium processing, and it is shipped between mills and refineries in this form.

What is noted about the long-term stability of U₃O₈?

U₃O₈ has potential long-term stability in a geologic environment, suggesting it is a durable compound for storage or disposal.

How can uranium dioxide (UO₂) be oxidized to Triuranium octoxide (U₃O₈)?

Uranium dioxide (UO₂) is oxidized to U₃O₈ in the presence of oxygen (O₂).

How is Triuranium octoxide (U₃O₈) formed from uranium trioxide (UO₃)?

Uranium trioxide (UO₃) loses oxygen at temperatures above 500 °C and is reduced to U₃O₈.

What are two common precursors used for the industrial production of Triuranium octoxide?

Triuranium octoxide can be produced by the calcination of ammonium diuranate or ammonium uranyl carbonate.

What is a potential use for Triuranium octoxide related to depleted uranium?

Due to its high stability, Triuranium octoxide can be used for the disposal of depleted uranium, a byproduct of uranium enrichment.

What is the purpose of converting Triuranium octoxide into uranium hexafluoride?

Triuranium octoxide is converted to uranium hexafluoride (UF₆) for the purpose of uranium enrichment, a critical step in preparing nuclear fuel.

Describe the industrial production of Triuranium octoxide from ammonium uranyl carbonate (AUC).

Industrially, Triuranium octoxide is produced by the calcination of ammonium uranyl carbonate or ammonium diuranate. The process involving AUC includes hydrolyzing uranium hexafluoride in water to form uranyl fluoride, precipitating this with ammonium carbonate, drying the resulting ammonium uranyl carbonate, and then heating it in air to convert it to U₃O₈.

Explain the chemical reactions involved in the formation of Triuranium octoxide from uranium dioxide and oxygen.

Triuranium octoxide is formed through a multi-step oxidation of uranium dioxide by oxygen gas. The sequence involves: 8 UO₂ + O₂ → 2 U₄O₉, followed by 6 U₄O₉ + O₂ → 8 U₃O₇, and finally 2 U₃O₇ + O₂ → 2 U₃O₈.

How can uranium trioxide (UO₃) be reduced to Triuranium octoxide (U₃O₈)?

Uranium trioxide (UO₃) can be reduced to U₃O₈ through calcination at high temperatures (e.g., 700°C) or by reaction with reducing agents like hydrogen gas at temperatures between 500°C and 700°C.

What other uranium oxides can be produced during the reduction of uranium trioxide with hydrogen?

The reduction of uranium trioxide with hydrogen gas can also produce other uranium oxides, such as U₄O₉ and UO₂.

What has been determined about the oxidation states of uranium in U₃O₈ based on absorption spectrum studies?

Studies on the absorption spectrum of U₃O₈ suggest that each formula unit contains two U(V) atoms and one U(VI) atom, with no U(IV) atoms present. This indicates a mixed oxidation state for uranium within the compound.

How is Triuranium octoxide reduced to uranium dioxide?

Triuranium octoxide can be reduced to uranium dioxide by reacting it with hydrogen gas. The chemical equation for this reaction is U₃O₈ + 2 H₂ → 3 UO₂ + 2 H₂O.

What happens to Triuranium octoxide at temperatures above 800°C regarding its oxygen content?

At temperatures above 800°C, Triuranium octoxide loses oxygen to form a non-stoichiometric compound (U₃O₈-z), but it recovers this oxygen when it returns to normal temperatures.

Under what conditions can Triuranium octoxide be converted to uranium trioxide (UO₃)?

Triuranium octoxide can be slowly oxidized to uranium trioxide (UO₃) under high pressures of oxygen, following the reaction: U₃O₈ + ½ O₂ → 3 UO₃.

What is the reaction of Triuranium octoxide with hydrofluoric acid at 250°C?

Triuranium octoxide reacts with hydrofluoric acid at 250°C to form uranyl fluoride, according to the reaction: U₃O₈ + 6 HF + ½ O₂ → 3 UO₂F₂ + 3 H₂O.

What is another method mentioned for reacting Triuranium octoxide to form uranyl chloride?

Triuranium octoxide can be reacted with a solution of hydrochloric acid and hydrogen peroxide to form uranyl chloride.

How many known polymorphs of Triuranium octoxide are mentioned, and what are their names?

Triuranium octoxide has multiple known polymorphs: α-U₃O₈, β-U₃O₈, γ-U₃O₈, and a non-stoichiometric high-pressure phase with the fluorite structure.

Which polymorph of Triuranium octoxide is most commonly encountered and stable under standard conditions?

The α-U₃O₈ polymorph is the most commonly encountered and is the most stable under standard conditions.

Describe the crystal structure of α-U₃O₈ at room temperature.

At room temperature, α-U₃O₈ has an orthorhombic pseudo-hexagonal structure with lattice constants a=6.72 Å, b=11.97 Å, and c=4.15 Å, belonging to the space group Amm2.

What is the crystal structure of α-U₃O₈ at higher temperatures?

At higher temperatures, around 350°C, α-U₃O₈ transitions into a true hexagonal structure with the space group P6̄2m.

How is the structure of α-U₃O₈ described in terms of layers and bonding?

α-U₃O₈ is composed of layers of uranium and oxygen atoms, with oxygen bridges connecting uranium atoms in different layers. Within each layer, uranium atoms are surrounded by five oxygen atoms, leading to a total of seven oxygen atoms bonded to each uranium atom.

What is the molecular geometry around the uranium atoms in α-U₃O₈?

Each uranium atom in α-U₃O₈ has a molecular geometry of pentagonal bipyramidal, as it is bonded to seven oxygen atoms.

How is the β-U₃O₈ polymorph formed?

The β-U₃O₈ polymorph can be formed by heating α-U₃O₈ to 1350°C and then slowly cooling it.

What is the space group and cell type for β-U₃O₈?

β-U₃O₈ has an orthorhombic cell with the space group Cmcm.

How does the arrangement of uranium and oxygen atoms differ between α-U₃O₈ and β-U₃O₈?

While both have layered structures, in β-U₃O₈, adjacent layers have different structures, with every other layer having the same arrangement of U and O atoms, unlike the consistent U-O structure in α-U₃O₈.

What are the different molecular geometries of uranium atoms found in β-U₃O₈?

In β-U₃O₈, two uranium atoms per formula unit have pentagonal bipyramidal molecular geometries, while the third uranium atom has a tetragonal bipyramidal molecular geometry.

Under what conditions is the γ-U₃O₈ polymorph formed?

The γ-U₃O₈ polymorph is formed at approximately 200-300°C and at 16,000 atmospheres of pressure.

What characterizes the high-pressure fluorite-type phase of U₃O₈?

The high-pressure fluorite-type phase of U₃O₈ is formed at pressures greater than 8.1 GPa, exhibits a hyperstoichiometric fluorite-type structure, and is 28% denser than α-U₃O₈.

What is the formula and structure type of the high-pressure U₃O₈ phase?

This high-pressure phase has a cubic structure with many defects and its formula is UO₂₊ₓ, where x is approximately 0.8.

In what natural mineral can Triuranium octoxide be found, and in what approximate concentration?

Triuranium octoxide can be found in small quantities, approximately 0.01-0.05%, in the mineral pitchblende.

What is the role of Triuranium octoxide in the 'dry' process for producing uranium hexafluoride?

In the 'dry' process for producing uranium hexafluoride, Triuranium octoxide is purified through calcination and then crushed before further processing.

Describe the initial steps of the 'wet' process for converting Triuranium octoxide into uranium hexafluoride.

The 'wet' process involves dissolving U₃O₈ in nitric acid to form uranyl nitrate, followed by calcining it to uranium trioxide in a fluidized bed reactor.

What are the subsequent chemical reactions involved in converting uranium oxides (like U₃O₈ or UO₃) to uranium hexafluoride (UF₆)?

The uranium oxide is first reduced using hydrogen gas to form uranium dioxide (UO₂). This UO₂ is then reacted with hydrofluoric acid (HF) to produce uranium tetrafluoride (UF₄), which is subsequently reacted with fluorine gas (F₂) to yield uranium hexafluoride (UF₆).

How is Triuranium octoxide utilized as a reference material?

Triuranium octoxide serves as a certified reference material and can be used to determine the impurity levels in a sample of uranium.

What are the primary health hazards associated with Triuranium octoxide?

Triuranium octoxide is a carcinogen and is toxic by inhalation and ingestion, particularly with repeated exposure. It can target the kidney, liver, lungs, and brain, and also causes irritation upon contact with skin and eyes.

Triuranium Octoxide Wiki: Uranium's Foundation: The Chemistry and Significance of Triuranium Octoxide

Dive in with Flashcard Learning!

When you are ready...
🎮 Play the Wiki2Web Clarity Challenge Game🎮

What is Triuranium Octoxide?

The Compound U₃O₈

Triuranium octoxide, chemically represented as U₃O₈, is a significant compound of uranium. It typically presents as an olive-green to black, odorless solid. This compound is widely recognized as one of the most stable and common forms of yellowcake, the intermediate product in uranium milling and refining processes, making it a crucial material in the nuclear fuel cycle.

Long-Term Stability

A key characteristic of U₃O₈ is its remarkable long-term stability, particularly within geological environments. This property makes it a preferred form for the disposal of depleted uranium, ensuring containment and minimizing environmental impact over extended periods. Its resilience is fundamental to its role in various stages of nuclear material management.

Chemical Transformation

Triuranium octoxide is formed through specific oxidation and reduction reactions involving other uranium compounds. For instance, uranium dioxide (UO₂) readily oxidizes to U₃O₈ in the presence of oxygen. Conversely, uranium trioxide (UO₃) loses oxygen at elevated temperatures to yield U₃O₈. It can also be synthesized via the calcination of precursor compounds like ammonium uranyl carbonate or ammonium diuranate.

Chemical and Physical Properties

Physical Characteristics

Triuranium octoxide possesses a notable density of 8.38 g/cm³. It exhibits a high melting point, approximately 1,150 °C (2,100 °F), though it decomposes upon further heating to 1,300 °C (2,370 °F). Its solubility in water is negligible, classifying it as insoluble. However, it readily dissolves in strong mineral acids such as nitric acid and sulfuric acid.

Molar Mass and Entropy

The molar mass of U₃O₈ is calculated to be 842.08 g/mol. Thermodynamically, its standard molar entropy (S°₂₉₈) is 282 J·mol⁻¹·K⁻¹, indicating a moderate degree of disorder in its standard state. The standard enthalpy of formation (ΔfH°₂₉₈) is -3575 kJ·mol⁻¹, reflecting its stability as a compound.

Oxidation States

While the precise oxidation states within U₃O₈ have been a subject of study, spectroscopic analysis suggests the presence of both Uranium(V) (U^V) and Uranium(VI) (U^VI) species. Specifically, each formula unit is understood to contain two U^V atoms and one U^VI atom, without any U^IV present. This mixed-valence state contributes to its unique chemical behavior.

Industrial Production Pathways

Calcination of Precursors

The industrial production of Triuranium octoxide primarily involves the calcination (high-temperature heating) of uranium precursor compounds. Common methods utilize ammonium uranyl carbonate (AUC) or ammonium diuranate. These processes are carefully controlled to ensure the desired U₃O₈ stoichiometry and purity.

A typical pathway involves the hydrolysis of uranium hexafluoride (UF₆) to uranyl fluoride (UO₂F₂), followed by precipitation with ammonium carbonate to form ammonium uranyl carbonate:

UF₆(g) + 2 H₂O(l) → UO₂F₂(aq) + 4 HF(aq)
UO₂F₂(aq) + 3 (NH₄)₂CO₃ → (NH₄)₄UO₂(CO₃)₃ + 2 NH₄F

The dried ammonium uranyl carbonate is then heated in air, yielding U₃O₈:

3 (NH₄)₄UO₂(CO₃)₃ → U₃O₈ + 4 NH₃ + 5 CO₂ + 2 H₂O + ½ O₂

Alternatively, direct oxidation of uranium dioxide (UO₂) by oxygen gas at approximately 250°C proceeds through intermediate oxides:

8 UO₂ + O₂ → 2 U₄O₉
6 U₄O₉ + O₂ → 8 U₃O₇
2 U₃O₇ + O₂ → 2 U₃O₈

Crystal Structures of U₃O₈

Alpha (α) Polymorph

The most stable and commonly encountered form is α-U₃O₈. At ambient temperatures, it crystallizes in a pseudo-hexagonal orthorhombic structure (space group Amm2) with lattice constants a=6.72 Å, b=11.97 Å, and c=4.15 Å. Upon heating to around 350 °C, it transitions to a true hexagonal structure (space group P6̄2m). This structure features layered arrangements of uranium and oxygen atoms, with uranium atoms typically exhibiting pentagonal bipyramidal coordination.

Beta (β) Polymorph

The β-U₃O₈ phase can be obtained by heating α-U₃O₈ to 1350 °C followed by slow cooling. It retains an orthorhombic cell (space group Cmcm) with similar lattice constants to the alpha phase. The structural differences involve the arrangement of uranium and oxygen atoms between layers, and the coordination geometry around uranium atoms, where some U atoms adopt a tetragonal bipyramidal geometry.

Gamma (γ) and Fluorite-Type Phases

The γ-U₃O₈ phase is reported to form under specific high-temperature and high-pressure conditions (around 200-300 °C and 16,000 atm), though detailed information is limited. Additionally, a high-pressure phase exhibiting a fluorite-type structure is formed above 8.1 GPa. This phase is significantly denser and possesses a cubic structure with considerable crystallographic defects, often represented as UO₂₊ₓ where x ≈ 0.8.

Applications and Significance

Nuclear Fuel Cycle

Triuranium octoxide is a critical intermediate in the nuclear fuel cycle. It is converted into uranium hexafluoride (UF₆), the gaseous compound used in the process of uranium enrichment. This enrichment separates fissile uranium-235 from the more abundant uranium-238, a necessary step for producing nuclear reactor fuel and other nuclear materials.

The conversion typically involves several steps:

Purification and Reduction: U₃O₈ is purified and then reduced to uranium dioxide (UO₂) using hydrogen gas at elevated temperatures.
```
U₃O₈ + 2 H₂ → 3 UO₂ + 2 H₂O
```
Hydrofluorination: Uranium dioxide is reacted with hydrofluoric acid (HF) to produce uranium tetrafluoride (UF₄).
```
UO₂ + 4 HF → UF₄ + 2 H₂O
```
Fluorination: Finally, uranium tetrafluoride is reacted with fluorine gas (F₂) to yield uranium hexafluoride (UF₆).
```
UF₄ + F₂ → UF₆
```
This UF₆ is then suitable for isotopic separation via gaseous diffusion or gas centrifugation.

Reference Material

Due to its well-defined composition and stability, Triuranium octoxide serves as a certified reference material (CRM). CRMs are essential for calibrating analytical instruments and validating measurement methods used in quality control and regulatory compliance within the nuclear industry and research laboratories. It helps ensure the accuracy of uranium concentration and impurity analysis in various samples.

Geological Repository Stability

As mentioned, the inherent stability of U₃O₈ in geological environments makes it a valuable material for long-term waste management strategies. Its resistance to chemical alteration and leaching contributes to the safety case for deep geological repositories designed for radioactive waste disposal.

Health and Safety Considerations

Chemical Toxicity

Triuranium octoxide is classified as a carcinogen and is toxic, particularly through inhalation and ingestion, especially with repeated exposure. If absorbed into the body, it can target vital organs including the kidneys, liver, lungs, and brain. Direct contact may cause irritation to the skin and eyes. Consequently, handling U₃O₈ requires stringent safety protocols, including adequate ventilation and appropriate personal protective equipment.

Radioactivity

Beyond its chemical toxicity, U₃O₈ is inherently radioactive. It primarily emits alpha particles, which have a short range but can be highly damaging if the radioactive material is internalized. This radioactivity necessitates specialized handling procedures, shielding, and monitoring to minimize radiation exposure risks for personnel and the environment.

Safe Handling Practices

Given its hazardous properties, working with Triuranium octoxide demands adherence to strict safety guidelines. This includes working in designated areas with controlled access, utilizing fume hoods or glove boxes for containment, employing appropriate respiratory protection, and implementing robust waste management procedures. Compliance with regulatory standards for radioactive and toxic materials is paramount.

Teacher's Corner

Edit and Print this course in the Wiki2Web Teacher Studio

Edit and Print Materials from this study in the wiki2web studio

Click here to open the "Triuranium Octoxide" Wiki2Web Studio curriculum kit

Use the free Wiki2web Studio to generate printable flashcards, worksheets, exams, and export your materials as a web page or an interactive game.

True or False?

Test Your Knowledge!

Gamer's Corner

Are you ready for the Wiki2Web Clarity Challenge?

Learn about triuranium_octoxide while playing the wiki2web Clarity Challenge game.

Unlock the mystery image and prove your knowledge by earning trophies. This simple game is addictively fun and is a great way to learn!

Play now

Explore More Topics

Discover other topics to study!

boso margrave of tuscany

archdiocese of vaduz

george monck 1st duke of albemarle

university of manchester

kurultai

palestinian political violence

References

WebElements, https://www.webelements.com

A full list of references for this article are available at the Triuranium octoxide Wikipedia page

Feedback & Support

To report an issue with this page, or to find out ways to support the mission, please click here.

Important Disclaimers

AI-Generated Content Advisory

This document has been generated by an Artificial Intelligence model. While efforts have been made to ensure accuracy and adherence to the provided source material, it is intended for informational and educational purposes only. The content is based on a snapshot of publicly available data and may not reflect the most current scientific understanding or all nuances of the subject matter.

This is not professional advice. The information presented here does not constitute expert advice in nuclear chemistry, material science, or radiation safety. Handling radioactive materials like Triuranium Octoxide requires specialized training, equipment, and adherence to strict regulatory protocols. Always consult with qualified professionals and refer to official safety documentation and regulatory guidelines before engaging with such materials.

The creators of this page are not liable for any errors, omissions, or consequences arising from the use of this information. Users are solely responsible for their actions and interpretations.

Uranium's Foundation

💡 Dive in with Flashcard Learning! 💡

What is Triuranium Octoxide? ℹ️

⚛️ The Compound U₃O₈

⏳ Long-Term Stability

🧪 Chemical Transformation

Chemical and Physical Properties 🔬

📏 Physical Characteristics

⚖️ Molar Mass and Entropy

⚡ Oxidation States

Industrial Production Pathways 🏭

⚙️ Calcination of Precursors

Crystal Structures of U₃O₈ 💎

á Alpha (α) Polymorph

β Beta (β) Polymorph

γ Gamma (γ) and Fluorite-Type Phases

Applications and Significance ⚛️

⛽ Nuclear Fuel Cycle

📏 Reference Material

🌍 Geological Repository Stability

Health and Safety Considerations ⚠️

☠️ Chemical Toxicity

☢️ Radioactivity

⛑️ Safe Handling Practices

Teacher's Corner 🧑‍🏫

Edit and Print this course in the Wiki2Web Teacher Studio

True or False? 🤔

❓ Test Your Knowledge! ❓

Gamer's Corner 🎮

Are you ready for the Wiki2Web Clarity Challenge?

Explore More Topics

📜 Discover other topics to study!

References

📜 References

Feedback & Support 👍

To report an issue with this page, or to find out ways to support the mission, please click here.

Important Disclaimers 📜

❗ AI-Generated Content Advisory

Dive in with Flashcard Learning!

What is Triuranium Octoxide?

The Compound U₃O₈

Long-Term Stability

Chemical Transformation

Chemical and Physical Properties

Physical Characteristics

Molar Mass and Entropy

Oxidation States

Industrial Production Pathways

Calcination of Precursors

Crystal Structures of U₃O₈

Alpha (α) Polymorph

Beta (β) Polymorph

Gamma (γ) and Fluorite-Type Phases

Applications and Significance

Nuclear Fuel Cycle

Reference Material

Geological Repository Stability

Health and Safety Considerations

Chemical Toxicity

Radioactivity

Safe Handling Practices

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Important Disclaimers

AI-Generated Content Advisory