chemistry

Lanthanum carbide

Lanthanum carbide 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 Lanthanum carbide rather than just read about it. In short: Lanthanum carbide (LaC2) is a chemical compound. It is being studied in relation to the manufacture of certain types of superconductors and nanotubes.

Key takeaways

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

Reference excerpt

Lanthanum carbide (LaC2) is a chemical compound. It is being studied in relation to the manufacture of certain types of superconductors and nanotubes.

Preparation LaC2 can be prepared by reacting lanthanum oxide, La2O3, with carbon in an electric furnace, or by melting pellets of the elements in an arc furnace.

Properties LaC2 reacts with water to form acetylene, C2H2 and a mixture of complex hydrocarbons. LaC2 is a metallic conductor, in contrast to CaC2 which is an insulator. The crystal structure of LaC2 shows that it contains C2 units with a C-C bond length of 130.3 pm, which is longer than the C-C bond length in calcium carbide, 119.2 pm, which is close to that of ethyne. The structure of LaC2 can be described as La3+C22−(e-) where the electron enters the conduction band and antibonding orbitals on the C2 anion, increasing the bond length. This is analogous to the bonding present in the nitridoborate, CaNiBN.

Lanthanum carbide in carbon nano structures A method for making macroscopic quantities of C60 and the confirmation of the hollow, cagelike structures was published in 1990 by Kratschmer and co-workers. This was followed by the publication of methods for higher fullerenes (C70 and higher). In 1993, scientists discovered how to make a compound which is not as susceptible to moisture and air. They made containers to hold buckminsterfullerenes, or buckyballs; therefore they nicknamed the containers ‘buckyjars’. A few US patents were issued to universities in the mid-1990s; experiments with manufacturing techniques have continued at universities around the globe, including India, Japan, and Sweden.

Lanthanum atoms caged in fullerenes In La@C72, the lanthanum appears to stabilize the C72 carbon cage. A 1998 study by Stevenson et al. verified the presence of La@C72 as well as La2@C72, but empty-cage C72 was absent, based on laser desorption mass spectrometry and UV−vis spectroscopy. A 2008 study by Lu et al. showed that La2C72 do not adhere to the isolated pentagon rule (IPR), but has two pairs of fused pentagons at each pole of the cage and that the two La atoms reside close to the two fused-pentagon pairs. This result lends additional support to the idea that the carbon cage is stabilized by the La atoms. In addition to the properties included in the table at right, the magnetic properties of bulk amounts of La@C82 (isolated from various hollow fullerenes) have been tested. Magnetization data for an isolated La@C82 isomer were obtained using a SQUID magnetometer at temperatures ranging from 3 to 300 K. For La@C82 the inverse susceptibility as a function of temperature was observed to follow a Curie-Weiss law. The effective magnetic moment per La@C82 was found to be 0.38μB. Lanthanum carbide has also shown superconductive properties when converted into a layered lanthanum carbide halide La2C2X2 (X=Br,I). Investigations using high-resolution neutron powder diffraction measurements from room temperature to 1.5 Kelvin showed that it has superconductive properties at about 7.03 Kelvin for X=Br and at about 1.7 Kelvin for X=I, respectively.

References

External links MIT Open Courseware 3.091 – Introduction to Solid State Chemistry 2001 US Patent – Carbide nanomaterials. 1997 US Patent – Storage of hydrogen in layered nanostructures. 1996 US Patent – Metal, alloy, or metal carbide nanoparticles and a process for forming same. 1995 US Patent – Magnetic metal or metal carbide nanoparticles and a process for forming same.

Illustrations

Worked examples

Example 1 — a first encounter with Lanthanum carbide

Start with the simplest possible case. Write down what Lanthanum carbide 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 Lanthanum carbide 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 Lanthanum carbide 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 Lanthanum carbide

In research: Lanthanum carbide 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 Lanthanum carbide 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: Lanthanum carbide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acetylides, Carbides, Electrides, so understanding it makes those chapters shorter.
In everyday life: Look for Lanthanum carbide 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 Lanthanum carbide in 20 minutes

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

Frequently asked questions

What is Lanthanum carbide in simple terms?

Lanthanum carbide (LaC2) is a chemical compound. It is being studied in relation to the manufacture of certain types of superconductors and nanotubes.

Why does Lanthanum carbide 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 Lanthanum carbide?

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 Lanthanum carbide.