Lithium nitrite

Key takeaways

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

Reference excerpt

Lithium nitrite is the lithium salt of nitrous acid, with formula LiNO2. This compound is hygroscopic and very soluble in water. It is used as a corrosion inhibitor in mortar. It is also used in the production of explosives, due to its ability to nitrosate ketones under certain conditions.

Preparation Lithium nitrate (LiNO3) will undergo thermal decomposition above 500 °C to yield the evolution of lithium nitrite and oxygen as in the following reaction:

2 LiNO3 → 2 LiNO2 + O2 (at ~500 °C) Lithium nitrite can also be prepared by the reaction of nitric oxide (NO) with lithium hydroxide (LiOH) as shown below:

4 NO + 2 LiOH → 2 LiNO2 + N2O + H2O 6 NO + 4 LiOH → 4 LiNO2 + N2 + 2 H2O

Crystallization and crystal structure Lithium nitrite crystals can be obtained most efficiently by reacting lithium sulfate and barium nitrite in an aqueous solution. However, these crystals can also be prepared by mixing equal amounts of lithium sulfate and potassium nitrite in highly concentrated aqueous solution. This is followed by considerable evaporation and filtration, which removes the resulting precipitate of potassium sulfate and lithium potassium sulfate after further evaporation and extraction with absolute alcohol. Lithium nitrite is exceptionally soluble in absolute alcohol. However, potassium nitrite is not very soluble. This makes absolute alcohol a choice solvent for the crystallization of lithium nitrite because the crystals can be extracted in a substantially pure state. The alcoholic solution will leave a white residue of small crystals upon evaporation. The addition of a small amount of water to this residue will yield the larger needle-shaped crystals of lithium nitrite monohydrate (LiNO2·H2O). The above methods will result in flat, needle-shaped crystals. These crystals are white and typically 1–2 cm. in length. Below 100 °C, these crystals will melt in their own water of crystallization and will tend to lose water slowly. Rapid dehydration will occur at temperatures above 160 °C as well as a minuscule loss of nitrogen oxide. This rapid dehydration leaves behind a residue which consists almost entirely of the anhydrous salt. This anhydrous salt is extraordinarily soluble in water and will readily form a supersaturated solution. Monohydrate crystals will deposit from this supersaturated solution upon cooling or with the addition of ready formed salt crystals.

Industrial uses Reinforcement bars, ready mixed concrete materials, and repair materials are often subject to corrosion. These resources will rapidly degrade due to chloride attack and carbonatation. This not only affects the service lives of such materials, but it also requires a considerable cost for the repair of such defects. Lithium nitrite and calcium nitrite are generally used in the construction industry as a means to protect reinforced concrete structures from corrosion. Unlike calcium nitrite inhibitors, lithium nitrite is particularly valued for corrosion inhibition and resistance of carbonation when an accelerated hardening process is not used and when a high concentration of 10% or more cement is added by weight. Generally speaking, studying the effectiveness of such inhibitors has been done using destructive methods. These studies require placing specimens to accelerated corrosion and measuring the degree of corrosion. "However, it is extremely difficult to measure the effect of corrosion inhibitors in actual structures using a destructive method." Recently, sensors that can measure changes in electrical resistance due to the corrosion in iron and thus indicate the degree of corrosion of a material have been developed. These sensors provide a non-destructive way to evaluate the degree of corrosion in concrete materials. Therefore, the effect of lithium nitrite as a corrosion inhibitor has also been studied by non-destructive means. A study was conducted in Korea to experimentally determine the most effective dose and performance of lithium nitrite corrosion inhibitors. This experiment employed the molar ratio of nitrite ions to chloride ions (NO2−/Cl−) as a test parameter. This study concluded that a lithium nitrite dosage of 0.6 in the nitrite-chloride ion molar ratio is a successful dosage for mortar containing chlorides.

References

Cited sources Haynes, William M., ed. (2016). CRC Handbook of Chemistry and Physics (97th ed.). CRC Press. ISBN 9781498754293.

Illustrations

Worked examples

Example 1 — a first encounter with Lithium nitrite

Start with the simplest possible case. Write down what Lithium nitrite claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Lithium nitrite 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 Lithium nitrite 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 Lithium nitrite

In research: Lithium nitrite appears in science 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 Lithium nitrite 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: Lithium nitrite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Corrosion inhibitors, Lithium salts, Nitrites, so understanding it makes those chapters shorter.
In everyday life: Look for Lithium nitrite 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.

How to study Lithium nitrite in 20 minutes

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

Frequently asked questions

What is Lithium nitrite in simple terms?

Lithium nitrite is the lithium salt of nitrous acid, with formula LiNO2. This compound is hygroscopic and very soluble in water.

Why does Lithium nitrite matter?

Because it connects several science 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 Lithium nitrite?

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 Lithium nitrite.