chemistry

Nickel(II) hydroxide

Nickel(II) hydroxide 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 Nickel(II) hydroxide rather than just read about it. In short: Nickel(II) hydroxide is the inorganic compound with the formula Ni(OH)2. It is a lime-green solid that dissolves with decomposition in ammonia and amines and is attacked by acids.

Key takeaways

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

Reference excerpt

Nickel(II) hydroxide is the inorganic compound with the formula Ni(OH)2. It is a lime-green solid that dissolves with decomposition in ammonia and amines and is attacked by acids. It is electroactive, being converted to the Ni(III) oxy-hydroxide, leading to widespread applications in rechargeable batteries.

Properties Nickel(II) hydroxide has two well-characterized polymorphs, α and β. The α structure consists of Ni(OH)2 layers with intercalated anions or water. The β form adopts a hexagonal close-packed structure of Ni2+ and OH− ions. In the presence of water, the α polymorph typically recrystallizes to the β form. In addition to the α and β polymorphs, several γ nickel hydroxides have been described, distinguished by crystal structures with much larger inter-sheet distances.

Occurrence The mineral form of Ni(OH)2, theophrastite, was first identified in the Vermion region of northern Greece, in 1980. It is found naturally as a translucent emerald-green crystal formed in thin sheets near the boundaries of idocrase or chlorite crystals. A nickel-magnesium variant of the mineral, (Ni,Mg)(OH)2 had been previously discovered at Hagdale on the island of Unst in Scotland.

Reactions Nickel(II) hydroxide is frequently used in electrical car batteries. Specifically, Ni(OH)2 readily oxidizes to nickel oxyhydroxide, NiOOH, in combination with a reduction reaction, often of a metal hydride (reaction 1 and 2). Reaction 1 Ni(OH)2 + OH− → NiO(OH) + H2O + e− Reaction 2 M + H2O + e− → MH + OH− Net Reaction (in H2O) Ni(OH)2 + M → NiOOH + MH Of the two polymorphs, α-Ni(OH)2 has a higher theoretical capacity and thus is generally considered to be preferable in electrochemical applications. However, it transforms to β-Ni(OH)2 in alkaline solutions, leading to many investigations into the possibility of stabilized α-Ni(OH)2 electrodes for industrial applications.

Synthesis The synthesis entails treating aqueous solutions of nickel(II) salts with potassium hydroxide. When the same reaction is conducted in the presence of bromine, the product is Ni3O2(OH)4.

Toxicity The Ni2+ ion is a carcinogen when inhaled.

See also List of minerals named after people Nickel–cadmium battery Nickel–hydrogen battery Nickel–metal hydride battery Nickel–iron battery

References

Illustrations

Worked examples

Example 1 — a first encounter with Nickel(II) hydroxide

Start with the simplest possible case. Write down what Nickel(II) hydroxide 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 Nickel(II) hydroxide 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 Nickel(II) hydroxide 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 Nickel(II) hydroxide

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

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

Frequently asked questions

What is Nickel(II) hydroxide in simple terms?

Nickel(II) hydroxide is the inorganic compound with the formula Ni(OH)2. It is a lime-green solid that dissolves with decomposition in ammonia and amines and is attacked by acids.

Why does Nickel(II) hydroxide 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 Nickel(II) hydroxide?

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 Nickel(II) hydroxide.