chemistry

Magnesium compounds

Magnesium compounds 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 Magnesium compounds rather than just read about it. In short: Magnesium compounds are compounds formed by the element magnesium (Mg). These compounds are important to industry and biology, including magnesium carbonate, magnesium chloride, magnesium citrate, magnesium hydroxide (milk of magnesia), magnesium oxide, magnesium sulfate, and magnesium sulfate heptahydrate (Epsom salts).

Key takeaways

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

Reference excerpt

Magnesium compounds are compounds formed by the element magnesium (Mg). These compounds are important to industry and biology, including magnesium carbonate, magnesium chloride, magnesium citrate, magnesium hydroxide (milk of magnesia), magnesium oxide, magnesium sulfate, and magnesium sulfate heptahydrate (Epsom salts).

Inorganic compounds

Hydrides, halides and oxo-halides Magnesium hydride was first prepared in 1951 by the reaction between hydrogen and magnesium under high temperature, pressure and magnesium iodide as a catalyst. It reacts with water to release hydrogen gas; it decomposes at 287 °C, 1 bar:

MgH2 → Mg + H2 Magnesium can form compounds with the chemical formula MgX2 (X=F, Cl, Br, I) with halogens. Except for magnesium fluoride, the halides are easily soluble in water, but the solubility of magnesium fluoride is higher than that of other alkaline earth metal fluorides. High-purity magnesium fluoride is produced industrially by the reaction of magnesium sulfate and sodium fluoride, which sublimates at 1320 °C. Magnesium chloride is generally obtained by chlorination of magnesium oxide, or by reacting magnesium chloride hexahydrate with ammonium chloride under dry hydrogen chloride, and then thermally decomposing the resulting magnesium ammonium double salt. Its hydrate will be hydrolyzed, making the solution acidic; direct heating of the hydrate will give the hydrolyzed product:

[Mg(H2O)6]2+ → [Mg(H2O)5(OH)]+ + H3O+ (decomposes in water) MgCl2·nH2O → Mg(OH)Cl + HCl + (n-1)H2O (decomposes when heated) Magnesium chloride is an ionic compound, which can be electrolysed in a molten state to form magnesium and chlorine gas. The properties of magnesium bromide and magnesium iodide are similar. HMgX (X=Cl,Br,I) can be obtained by reacting the corresponding magnesium halide with magnesium hydride.

Magnesium hypochlorite and magnesium chlorite are unstable compounds, they are easy to hydrolyze, the former generates basic salt Mg(OCl)2·2Mg(OH)2 and the latter generates hydroxide Mg(OH)2; magnesium chlorate can be obtained by reacting magnesium carbonate with chloric acid and crystallizing hexahydrate from solution, which can also be obtained by reacting magnesium hydroxide with chlorine gas and extracted with acetone:

6 Mg(OH)2 + 6 Cl2 → 5 MgCl2 + Mg(ClO3)2 + 6 H2O Magnesium perchlorate is a white powder that is easily soluble in water, which can be obtained by the reaction of magnesium oxide and perchloric acid. The hexahydrate crystallizes from the solution, and then it is dried with phosphorus pentoxide in a vacuum at 200~250 °C to obtain the anhydrous form. It is a commonly used desiccant and can also be used as a Lewis acid or electrophile activator. Magnesium perbromate can also crystallize out of the solution to form the hexahydrate, which can be heated to obtain anhydrous, and the anhydrous is further heated, and it decomposes into magnesium oxide, bromine and oxygen.

Oxides and chalcogenides Magnesium oxide is the end product of the thermal decomposition of some magnesium compounds and is usually prepared by igniting carbonates or hydroxides. Magnesium hydroxide is a strong electrolyte, which can be obtained by the reaction of a soluble magnesium salt and sodium hydroxide. Like magnesium oxide, it will generate a basic carbonate when placed in the air. Magnesium sulfide can be produced by the reaction of magnesium and hydrogen sulfide, or by the reaction of magnesium sulfate and carbon disulfide at high temperature:

Mg + H2S → MgS + H2 3 MgSO4 + 4 CS2 → 3 MgS + 4 COS + 4 SO2 It can be hydrolyzed to Mg(HS)2, and further hydrolyzed to Mg(OH)2 at higher temperatures. A solution of magnesium hydrosulfide can also be prepared by reacting hydrogen sulfide with magnesium oxide in suspension. Magnesium polysulfides have been studied in magnesium-sulfur batteries. Magnesium selenide is more reactive than zinc selenide and decomposes in humid air; the properties of magnesium telluride and magnesium selenide are similar.

Organic compounds

Grignard reagent

The name of the Grignard reagent comes from the French chemist Victor Grignard who discovered it. This type of organomagnesium compound has the general formula R–Mg–X, where R is a hydrocarbon group and X is a halogen. They are usually coordinated with solvent molecules. bit. Grignard reagents can be obtained by reacting magnesium with halogenated hydrocarbons in a solvent. Since there is an oxide film on the surface of magnesium, iodine is generally added to accelerate the reaction. Grignard reagents are commonly used in organic synthesis to extend carbon chains:

Dihydrocarbylmagnesium Dihydrocarbylmagnesium is an organic compound with R–Mg–R’, which can be prepared by the reaction of dihydrocarbylmercury and magnesium. Their reactivity is similar to that of Grignard reagents, and they can react with oxygen, water, and ammonia. Magnesium anthracene is the product obtained from the reaction of magnesium and anthracene in tetrahydrofuran, which can be used to provide C14H102− carbanions, which react with electrophiles to obtain di-derivatives of hydrogen anthracene.

Applications Magnesium compounds, primarily magnesium oxide (MgO), are used as a refractory material in furnace linings for producing iron, steel, nonferrous metals, glass, and cement. Magnesium oxide and other magnesium compounds are also used in the agricultural, chemical, and construction industries. Magnesium oxide from calcination is used as an electrical insulator in fire-resistant cables. Other applications include:

Magnesium hydride is under investigation as a way to store hydrogen. Magnesium reacted with an alkyl halide gives a Grignard reagent, which is a very useful tool for preparing alcohols. Magnesium salts are included in various foods, fertilizers (magnesium is a component of chlorophyll), and microbe culture media. Magnesium sulfite is used in the manufacture of paper (sulfite process). Magnesium phosphate is used to fireproof wood used in construction. Magnesium hexafluorosilicate is used for moth-proofing textiles.

See also Sodium compounds Aluminium compounds Calcium compounds

References

External reading

Illustrations

Worked examples

Example 1 — a first encounter with Magnesium compounds

Start with the simplest possible case. Write down what Magnesium compounds 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 Magnesium compounds 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 Magnesium compounds 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 Magnesium compounds

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

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

Frequently asked questions

What is Magnesium compounds in simple terms?

Why does Magnesium compounds 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 Magnesium compounds?

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 Magnesium compounds.