chemistry

Uranyl hydroxide

Uranyl hydroxide is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Uranyl hydroxide rather than just read about it. In short: Uranyl hydroxide is a hydroxide of uranium with the chemical formula UO2(OH)2 in the monomeric form and [(UO2)2(OH)4]2- in the dimeric; both forms may exist in normal aqueous media. In aerobic conditions, up to 5 hydroxides can bind to uranyl ([(UO2)2(OH)5]3-).

Key takeaways

Uranyl hydroxide belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Uranyl hydroxide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Uranyl hydroxide from memory before moving on to harder problems.

Reference excerpt

Uranyl hydroxide is a hydroxide of uranium with the chemical formula UO2(OH)2 in the monomeric form and [(UO2)2(OH)4]2- in the dimeric; both forms may exist in normal aqueous media. In aerobic conditions, up to 5 hydroxides can bind to uranyl ([(UO2)2(OH)5]3-). Uranyl hydroxide hydrate is precipitated as a colloidal yellowcake from oxidized uranium liquors near neutral pH. Uranyl hydroxide was once used in glassmaking and ceramics in the colouring of the vitreous phases and the preparation of pigments for high temperature firing. The introduction of alkaline diuranates (like sodium diuranate) into glasses leads to yellow by transmission, green by reflection; moreover these glasses become dichroic and fluorescent under ultraviolet rays. Uranyl hydroxide is teratogenic and radioactive.

Formation The formation of uranyl hydroxide hydrate can occur via hydrated uranyl fluoride [(UO2F2)(H2O)]7·4H2O which is not stable at an elevated water vapor pressure. A complete loss of fluorine is undergone and the formation of uranyl hydroxide hydrate ([(UO2)4O(OH)6]·5H2O) occurs. This uranyl hydroxide species is structurally similar to the uranyl hydroxide hydrate minerals schoepite and metaschoepite. X-ray diffraction data was gathered and found that this species has expanded interlayer spacing suggesting there may be additional water molecules in between uranyl layers. Unlike metaschoepite, however, this species does not form UO2(OH)2 upon dehydration.

Reactions [UO2(OH)]+ + H2O → [(UO2(OH)(H2O)]+ [(UO2(OH)(H2O)]+ + H2O → [(UO2(OH)(H2O)2]+ UO2(OH)2 reacts with water in a hydration reaction to form [(UO2(OH)2)(H2O)]+ and the monohydrate form also reacted with water to form dihydrates [(UO2OH)(H2O)2]+ and trihydrates [(UO2OH)(H2O)3]+. The hydration reaction to form the monohydrate was significantly slower than if the hydroxide were replaced with acetate or nitrate. This could be due to the strongly basic (OH)− reducing the Lewis acidity of U or because the more complex acetate and nitrate anions provide more degrees of freedom. However, it was found that the formation of the dihydrate uranyl hydroxide hydrate (2) was nearly three times faster than the monohydrate (1). A mechanism for oxygen exchange between the UO22+ cations in a highly alkaline solution was proposed and investigated by Shamov et al. in the Journal of the American Chemical Society. An equilibrium between [UO2(OH)4]2- and [UO2(OH)5]3- was observed followed by the formation of the stable [UO3(OH)3·H2O]3- intermediate that formed from [UO2(OH)5]3- via intramolecular water elimination.

References

The Structure of the a Form of Uranyl Hydroxide Alexander, C.A. (2005) "Volatilization of urania under strongly oxidizing conditions," Journal of Nuclear Materials, 346, 312–318.

Illustrations

Worked examples

Example 1 — a first encounter with Uranyl hydroxide

Start with the simplest possible case. Write down what Uranyl hydroxide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Uranyl hydroxide before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Uranyl hydroxide ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Uranyl hydroxide

In research: Uranyl hydroxide appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Uranyl hydroxide in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Uranyl hydroxide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hydroxides, Uranyl compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Uranyl hydroxide outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Uranyl hydroxide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Uranyl hydroxide means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Uranyl hydroxide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Uranyl hydroxide in simple terms?

Why does Uranyl hydroxide matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Uranyl hydroxide?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Uranyl hydroxide.