chemistry

Rubidium chloride

Rubidium 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 Rubidium chloride rather than just read about it. In short: Rubidium chloride is the chemical compound with the formula RbCl. This alkali metal halide salt is composed of rubidium and chlorine, and finds diverse uses ranging from electrochemistry to molecular biology.

Key takeaways

Rubidium 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 Rubidium chloride to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Rubidium chloride from memory before moving on to harder problems.

Reference excerpt

Rubidium chloride is the chemical compound with the formula RbCl. This alkali metal halide salt is composed of rubidium and chlorine, and finds diverse uses ranging from electrochemistry to molecular biology.

Structure In its gas phase, RbCl is diatomic with a bond length estimated at 2.7868 Å. This distance increases to 3.285 Å for cubic RbCl, reflecting the higher coordination number of the ions in the solid phase. Depending on conditions, solid RbCl exists in one of three arrangements or polymorphs as determined with holographic imaging:

Sodium chloride (octahedral 6:6) The sodium chloride (NaCl) polymorph is most common. A cubic close-packed arrangement of chloride anions with rubidium cations filling the octahedral holes describes this polymorph. Both ions are six-coordinate in this arrangement. The lattice energy of this polymorph is only 3.2 kJ/mol less than the following structure's.

Caesium chloride (cubic 8:8) At high temperature and pressure, RbCl adopts the caesium chloride (CsCl) structure (NaCl and KCl undergo the same structural change at high pressures). Here, the chloride ions form a simple cubic arrangement with chloride anions occupying the vertices of a cube surrounding a central Rb+. This is RbCl's densest packing motif. Because a cube has eight vertices, both ions' coordination numbers equal eight. This is RbCl's highest possible coordination number. Therefore, according to the radius ratio rule, cations in this polymorph will reach their largest apparent radius because the anion-cation distances are greatest.

Sphalerite (tetrahedral 4:4) The sphalerite polymorph of rubidium chloride has not been observed experimentally. This is consistent with the theory; the lattice energy is predicted to be nearly 40.0 kJ/mol smaller in magnitude than those of the preceding structures.

Synthesis and reaction The most common preparation of pure rubidium chloride involves the reaction of its hydroxide with hydrochloric acid, followed by recrystallization:

RbOH + HCl → RbCl + H2O Because RbCl is hygroscopic, it must be protected from atmospheric moisture, e.g. using a desiccator. RbCl is primarily used in laboratories. Therefore, numerous suppliers (see below) produce it in smaller quantities as needed. It is offered in a variety of forms for chemical and biomedical research. Rubidium chloride reacts with sulfuric acid to give rubidium hydrogen sulfate.

Radioactivity Every 18 mg of rubidium chloride is equivalent to approximately one banana equivalent dose due to the large fraction (27.8%) of naturally occurring radioactive isotope rubidium-87.

Uses Rubidium chloride is used as a gasoline additive to improve its octane number. Rubidium chloride has been shown to modify coupling between circadian oscillators via reduced photaic input to the suprachiasmatic nuclei. The outcome is a more equalized circadian rhythm, even for stressed organisms. Rubidium chloride is an excellent non-invasive biomarker. The compound dissolves well in water and can readily be taken up by organisms. Once broken in the body, Rb+ replaces K+ in tissues because they are from the same chemical group. An example of this is the use of a radioactive isotope to evaluate perfusion of heart muscle. Rubidium chloride transformation for competent cells is arguably the compound's most abundant use. Cells treated with a hypotonic solution containing RbCl expand. As a result, the expulsion of membrane proteins allows negatively charged DNA to bind. Rubidium chloride has shown antidepressant effects in experimental human studies, in doses ranging from 180 to 720 mg. It purportedly works by elevating dopamine and norepinephrine levels, resulting in a stimulating effect, which would be useful for anergic and apathetic depression.

References

Illustrations

Worked examples

Example 1 — a first encounter with Rubidium chloride

Start with the simplest possible case. Write down what Rubidium 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 Rubidium 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 Rubidium 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 Rubidium chloride

In research: Rubidium 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 Rubidium 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: Rubidium chloride is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alkali metal chlorides, Antidepressants, Chlorides, so understanding it makes those chapters shorter.
In everyday life: Look for Rubidium 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 Rubidium chloride in 20 minutes

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

Frequently asked questions

What is Rubidium chloride in simple terms?

Why does Rubidium 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 Rubidium 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 Rubidium chloride.