chemistry

Sodium tellurite

Sodium tellurite 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 Sodium tellurite rather than just read about it. In short: Sodium tellurite is an inorganic tellurium compound with formula Na2TeO3. It is a water-soluble white solid and a weak reducing agent.

Key takeaways

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

Reference excerpt

Sodium tellurite is an inorganic tellurium compound with formula Na2TeO3. It is a water-soluble white solid and a weak reducing agent. Sodium tellurite is an intermediate in the extraction of the element, tellurium; it is a product obtained from anode slimes and is a precursor to tellurium.

Preparation The main source of tellurium is from copper anode slimes, which contain precious metals as well as various tellurides. These slimes are roasted with sodium carbonate and oxygen to produce sodium tellurite.

Ag2Te + Na2CO3 + O2 → 2Ag + Na2TeO3 + CO2 (400–500 °C) This is a reaction with silver telluride. The telluride is oxidized to tellurite and the silver(I) is reduced to silver.

Purification The electrolysis of a tellurite solution yields purified tellurium.

Anode: 4OH− → 2H2O + O2 + 4e− Cathode: TeO32− + 3H2O + 4e− → Te + 6OH−

Structure and properties Tellurium has properties similar to sulfur and selenium. In the anhydrous form Na2TeO3 the tellurium atoms are 6 coordinate, three Te-O at 1.87 Å and three at 2.9 Å, with distorted octahedra sharing edges. In the pentahydrate, Na2TeO3.5H2O there are discrete tellurite anions, TeO32− which are pyramidal. The Te-O distance is 1.85 - 1.86 Å and the O-Te-O angle is close to 99.5°. The tellurite anion is a weak base. Sodium tellurite would be similar to sodium selenite and sodium sulfite. Sodium tellurite is both a weak oxidizing agent and a weak reducing agent.

Tellurite-related reactions H2TeO3 → H+ + HTeO3− pK 2.48 Telluric acid loses a proton at this pKa.

HTeO3− → H+ + TeO32− pK 7.7 Hydrogen tellurite loses a proton at this pKa to become the tellurite ion. This would happen in the reaction of tellurous acid with sodium hydroxide to make sodium tellurite.

TeO2 + 2OH− → TeO32− + H2O This is the reaction of tellurium dioxide with a base to make a tellurite salt.

Applications Sodium tellurite improves the corrosion resistance of electroplated nickel layers. Solutions of sodium tellurite are used for black or blue-black coatings on iron, steel, aluminum, and copper. In microbiology, sodium tellurite can be added to the growth medium to isolate bacteria with an inherent physiological resistance to its toxicity.

References

Cameo Chemicals. Sodium Tellurite. Retrieved March 8, 2009. Website: http://cameochemical.noaa.gov/chemical/5185. Knockaert, Guy (2002). "Tellurium and Tellurium Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a26_177.pub2. ISBN 978-3-527-30673-2.

Illustrations

Worked examples

Example 1 — a first encounter with Sodium tellurite

Start with the simplest possible case. Write down what Sodium tellurite 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 Sodium tellurite 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 Sodium tellurite 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 Sodium tellurite

In research: Sodium tellurite 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 Sodium tellurite 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: Sodium tellurite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Sodium compounds, Tellurites, so understanding it makes those chapters shorter.
In everyday life: Look for Sodium tellurite 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 Sodium tellurite in 20 minutes

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

Frequently asked questions

What is Sodium tellurite in simple terms?

Sodium tellurite is an inorganic tellurium compound with formula Na2TeO3. It is a water-soluble white solid and a weak reducing agent.

Why does Sodium tellurite 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 Sodium tellurite?

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 Sodium tellurite.