chemistry

Uranium hexachloride

Uranium hexachloride 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 Uranium hexachloride rather than just read about it. In short: Uranium hexachloride is the inorganic compound with the formula UCl6. It features uranium in the +6 oxidation state.

Key takeaways

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

Reference excerpt

Uranium hexachloride is the inorganic compound with the formula UCl6. It features uranium in the +6 oxidation state. UCl6 hydrolyzes readily but is stable under inert atmosphere. It is soluble in carbon tetrachloride (CCl4). It is a multi-luminescent dark green or black solid with a vapor pressure between 1-3 mmHg at 373.15 K.

Structure and bonding Uranium hexachloride has an octahedral geometry, with point group Oh. Its lattice (dimensions: 10.95 ± 0.02 Å x 6.03 ± 0.01 Å) is hexagonal in shape with three molecules per cell; the average theoretical U-Cl bond is 2.472 Å long (the experimental U-Cl length found by X-ray diffraction is 2.42 Å), and the distance between two adjacent chlorine atoms is 3.65 Å.

Chemical properties UCl6 is stable up to temperatures between 120 °C and 150 °C. The decomposition of UCl6 results in a solid phase transition from one crystal form of UCl6 to another more stable form, before fully decomposing into UCl5. It decomposes as follows:

2 UCl6 (g) → 2 UCl5 (s) + Cl2 (g) The activation energy for this reaction is about 40 kcal per mole.

Solubility UCl6 is not a very soluble compound. It dissolves in CCl4 to give a brown solution. It is slightly soluble in isobutyl bromide and in fluorocarbon (C7F16).

Reaction with hydrogen fluoride When treated with liquid hydrogen fluoride (HF) at room temperature, UCl6 produces UF5.

2 UCl6 + 10 HF → 2 UF5 + 10 HCl + Cl2

Synthesis Uranium hexachloride is efficiently prepared from uranium hexafluoride by halide exchange using boron trichloride according to the following idealized equation:

UF6 + 2 BCl3 → UCl6 + 2 BF3 Uranium hexachloride can also be synthesized from the reaction of uranium trioxide (UO3) with a mixture of liquid CCl4 and hot chlorine (Cl2). The yield can be increased if the reaction carried out in the presence of UCl5. The UO3 is converted to UCl5, which in turn reacts with the excess Cl2 to form UCl6. It requires a substantial amount of heat for the reaction to take place; the temperature range is from 65 °C to 170 °C depending on the amount of reactant (ideal temperature 100 °C - 125 °C). The reaction is carried out in a closed gas-tight vessel (for example a glovebox) that can withstand the pressure that builds up. Step 1: 2 UO3 + 5 Cl2 → 2 UCl5 + 3 O2 Step 2: 2 UCl5 + Cl2 → 2 UCl6 Overall reaction: 2 UO3 + 6 Cl2 → 2 UCl6 + 3 O2 This metal hexahalide also form upon combining Cl2 and UCl4 at 350 °C. Step 1: 2 UCl4 + Cl2 → 2 UCl5 Step 2: 2 UCl5 + Cl2 → 2 UCl6 Overall Reaction: UCl4 + Cl2 → UCl6

References

Illustrations

Worked examples

Example 1 — a first encounter with Uranium hexachloride

Start with the simplest possible case. Write down what Uranium hexachloride 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 Uranium hexachloride 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 Uranium hexachloride 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 Uranium hexachloride

In research: Uranium hexachloride 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 Uranium hexachloride 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: Uranium hexachloride is common in secondary-school and first-year university syllabi. It links to neighbouring topics Actinide halides, Chlorides, Uranium(VI) compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Uranium hexachloride 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 Uranium hexachloride in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Uranium hexachloride 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 Uranium hexachloride out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Uranium hexachloride in simple terms?

Uranium hexachloride is the inorganic compound with the formula UCl6. It features uranium in the +6 oxidation state.

Why does Uranium hexachloride 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 Uranium hexachloride?

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 Uranium hexachloride.