chemistry

Praseodymium(III) chloride

Praseodymium(III) chloride 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 Praseodymium(III) chloride rather than just read about it. In short: Praseodymium(III) chloride is the inorganic compound with the formula PrCl3. Like other lanthanide trichlorides, it exists both in the anhydrous and hydrated forms.

Key takeaways

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

Reference excerpt

Praseodymium(III) chloride is the inorganic compound with the formula PrCl3. Like other lanthanide trichlorides, it exists both in the anhydrous and hydrated forms. It is a blue-green solid that rapidly absorbs water on exposure to moist air to form a light green heptahydrate.

Preparation Praseodymium(III) chloride is prepared by treating praseodymium metal with hydrogen chloride:

2 Pr + 6 HCl → 2 PrCl3 + 3 H2 It is usually purified by vacuum sublimation. Hydrated salts of praseodymium(III) chloride can be prepared by treatment of either praseodymium metal or praseodymium(III) carbonate with hydrochloric acid:

Pr2(CO3)3 + 6 HCl + 15 H2O → 2 [Pr(H2O)9]Cl3 + 3 CO2 PrCl3∙7H2O is a hygroscopic substance, that will not crystallize from the mother liquor unless it is left to dry in a desiccator. Anhydrous PrCl3 can be made by thermal dehydration of the hydrate at 400 °C in the presence of ammonium chloride, the so-called ammonium chloride route. Alternatively the hydrate can be dehydrated using thionyl chloride.

Reactions Praseodymium(III) chloride is Lewis acidic, classified as "hard" according to the HSAB concept. Rapid heating of the hydrate may cause small amounts of hydrolysis. PrCl3 forms a stable Lewis acid-base complex K2PrCl5 by reaction with potassium chloride; this compound shows interesting optical and magnetic properties. Aqueous solutions of praseodymium(III) chloride can be used to prepare insoluble praseodymium(III) compounds. For example, praseodymium(III) phosphate and praseodymium(III) fluoride can be prepared by reaction with potassium phosphate and sodium fluoride, respectively:

PrCl3 + K3PO4 → PrPO4 + 3 KCl PrCl3 + 3 NaF → PrF3 + 3 NaCl 2PrCl3 + 3 Na2CO3----> Pr2CO3 + 6NaCl When heated with alkali metal chlorides, it forms a series of ternary (compounds containing three different elements) materials with the formulae MPr2Cl7, M3PrCl6, M2PrCl5, and M3Pr2Cl9 where M = K, Rb, Cs.

References

Further reading CRC Handbook of Chemistry and Physics (58th edition), CRC Press, West Palm Beach, Florida, 1977. N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Pergamon Press, 1984. S. Sugiyama, T. Miyamoto, H. Hayashi, M. Tanaka, J. B. Moffatt, "Effects of chlorine additives in the gas- and solid-phases on the oxidative dehydrogenation of ethane over praseodymium oxide", Journal of Molecular Catalysis A, 118, 129-136 (1997). Druding L. F.; Corbett J. D.; Ramsey B. N. (1963). "Rare Earth Metal-Metal Halide Systems. VI. Praseodymium Chloride". Inorganic Chemistry. 2 (4): 869–871. doi:10.1021/ic50008a055.

Illustrations

Worked examples

Example 1 — a first encounter with Praseodymium(III) chloride

Start with the simplest possible case. Write down what Praseodymium(III) chloride 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 Praseodymium(III) chloride 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 Praseodymium(III) chloride 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 Praseodymium(III) chloride

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

Read the reference excerpt below once, without taking notes.
Close the page and write down what Praseodymium(III) chloride 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.
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Frequently asked questions

What is Praseodymium(III) chloride in simple terms?

Praseodymium(III) chloride is the inorganic compound with the formula PrCl3. Like other lanthanide trichlorides, it exists both in the anhydrous and hydrated forms.

Why does Praseodymium(III) chloride 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 Praseodymium(III) chloride?

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 Praseodymium(III) chloride.