chemistry

Manganese(II) chloride

Manganese(II) 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 Manganese(II) chloride rather than just read about it. In short: Manganese(II) chloride is the dichloride salt of manganese, MnCl2. This inorganic chemical exists in the anhydrous form, as well as the dihydrate (MnCl2·2H2O) and tetrahydrate (MnCl2·4H2O), with the tetrahydrate being the most common form.

Key takeaways

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

Reference excerpt

Manganese(II) chloride is the dichloride salt of manganese, MnCl2. This inorganic chemical exists in the anhydrous form, as well as the dihydrate (MnCl2·2H2O) and tetrahydrate (MnCl2·4H2O), with the tetrahydrate being the most common form. Like many Mn(II) species, these salts are pink, with the paleness of the color being characteristic of transition metal complexes with high spin d5 configurations.

Preparation Manganese chloride is produced by treating manganese(IV) oxide with concentrated hydrochloric acid.

MnO2 + 4 HCl → MnCl2 + 2 H2O + Cl2 In the 19th century this reaction was used for the manufacture of chlorine. By carefully neutralizing the resulting solution with MnCO3, one can selectively precipitate iron salts, which are common impurities in manganese dioxide. In the laboratory, manganese chloride can be prepared by treating manganese metal or manganese(II) carbonate with hydrochloric acid:

Mn + 2 HCl + 4 H2O → MnCl2(H2O)4 + H2 MnCO3 + 2 HCl + 3 H2O → MnCl2(H2O)4 + CO2

Structures Anhydrous MnCl2 adopts a layered cadmium chloride-like structure. The tetrahydrate consists of octahedral cis-Mn(H2O)4Cl2 molecules. The trans isomer, which is metastable, is also known. The dihydrate MnCl2(H2O)2 is a coordination polymer. Each Mn center is coordinated to four doubly bridging chloride ligands. The octahedron is completed by a pair of mutually trans aquo ligands.

Chemical properties The hydrates dissolve in water to give mildly acidic solutions with a pH of around 4. These solutions consist of the metal aquo complex [Mn(H2O)6]2+. It is a weak Lewis acid, reacting with chloride ions to produce a series of salts containing the following ions [MnCl3]−, [MnCl4]2−, and [MnCl6]4−. Upon treatment with typical organic ligands, manganese(II) undergoes oxidation by air to give Mn(III) complexes. Examples include [Mn(EDTA)]−, [Mn(CN)6]3−, and [Mn(acetylacetonate)3]. Triphenylphosphine forms a labile 2:1 adduct:

MnCl2 + 2 Ph3P → [MnCl2(Ph3P)2] Anhydrous manganese(II) chloride serves as a starting point for the synthesis of a variety of organomanganese compounds. For example, manganocene is prepared by reaction of MnCl2 with a solution of sodium cyclopentadienide in tetrahydrofuran (THF).

MnCl2 + 2 NaC5H5 → Mn(C5H5)2 + 2 NaCl Similar reactions are used in the preparation of the antiknock compound methylcyclopentadienyl manganese tricarbonyl. Manganese chloride is a precursor to organomanganese reagents in organic chemistry. Manganese chloride is mainly used in the production of dry cell batteries.

Magnetism Manganese(II) salts are paramagnetic. As such the presence of such salts profoundly affect NMR spectra.

Natural occurrence Scacchite is the natural, anhydrous form of manganese(II) chloride.

Precautions Manganism, or manganese poisoning, can be caused by long-term exposure to manganese dust or fumes.

References

External links

National Pollutant Inventory: Manganese and compounds Fact Sheet

Illustrations

Worked examples

Example 1 — a first encounter with Manganese(II) chloride

Start with the simplest possible case. Write down what Manganese(II) 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 Manganese(II) 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 Manganese(II) 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 Manganese(II) chloride

In research: Manganese(II) 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 Manganese(II) 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: Manganese(II) chloride is common in secondary-school and first-year university syllabi. It links to neighbouring topics Chlorides, Manganese(II) compounds, Metal halides, so understanding it makes those chapters shorter.
In everyday life: Look for Manganese(II) 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 Manganese(II) chloride in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Manganese(II) chloride means in your own words.
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Work through the three examples above with pen and paper.
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Frequently asked questions

What is Manganese(II) chloride in simple terms?

Why does Manganese(II) 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 Manganese(II) 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 Manganese(II) chloride.