chemistry

Reinecke's salt

Reinecke's salt 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 Reinecke's salt rather than just read about it. In short: Reinecke's salt is an inorganic compound with the formula NH4[Cr(NCS)4(NH3)2·H2O. The dark-red crystalline compound is soluble in boiling water, acetone, and ethanol.

Key takeaways

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

Reference excerpt

Reinecke's salt is an inorganic compound with the formula NH4[Cr(NCS)4(NH3)2·H2O. The dark-red crystalline compound is soluble in boiling water, acetone, and ethanol. It can be classified as a metal isothiocyanate complex.

Structure, preparation, reactions The chromium atom is surrounded by six nitrogen atoms in an octahedral geometry. The NH3 ligands are mutually trans and the Cr-NCS groups are linear. The salt crystallizes with one molecule of water. It was first reported in 1863. NH4[Cr(NCS)4(NH3)2 is prepared by treatment of molten NH4SCN (melting point around 145–150 °C (293–302 °F)) with (NH4)2Cr2O7. This salt was once widely used to precipitate primary and secondary amines as their ammonium salts. Included in the amines that effectively form crystalline precipitates are those derived from the amino acids, including proline and hydroxyproline. It also reacts with Hg+2 compounds, giving a red color or a red precipitate.

References

Illustrations

Worked examples

Example 1 — a first encounter with Reinecke's salt

Start with the simplest possible case. Write down what Reinecke's salt 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 Reinecke's salt 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 Reinecke's salt 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 Reinecke's salt

In research: Reinecke's salt 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 Reinecke's salt 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: Reinecke's salt is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ammine complexes, Ammonium compounds, Chromium(III) compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Reinecke's salt 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 Reinecke's salt in 20 minutes

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

Frequently asked questions

What is Reinecke's salt in simple terms?

Reinecke's salt is an inorganic compound with the formula NH4[Cr(NCS)4(NH3)2·H2O. The dark-red crystalline compound is soluble in boiling water, acetone, and ethanol.

Why does Reinecke's salt 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 Reinecke's salt?

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 Reinecke's salt.