chemistry

Iron(II) nitrate

Iron(II) nitrate 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 Iron(II) nitrate rather than just read about it. In short: Iron(II) nitrate is the nitrate salt of iron(II). It is commonly encountered as the green hexahydrate, Fe(NO3)2·6H2O, which is a metal aquo complex, however it is not commercially available unlike iron(III) nitrate due to its instability to air.

Key takeaways

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

Reference excerpt

Iron(II) nitrate is the nitrate salt of iron(II). It is commonly encountered as the green hexahydrate, Fe(NO3)2·6H2O, which is a metal aquo complex, however it is not commercially available unlike iron(III) nitrate due to its instability to air. The salt is soluble in water and serves as a ready source of ferrous ions.

Structure No structure of any salt Fe(NO3)2·xH2O has been determined by X-ray crystallography. Nonetheless, the nature of the aquo complex [Fe(H2O)6]2+ is well known and relatively insensitive to the anion. The Fe-O distances are longer for [Fe(H2O)6]2+ (2.13 Å) than for the ferric analogue [Fe(H2O)6]3+ (1.99 Å). Both [Fe(H2O)6]n+ complexes are high spin, which results in pale colors, paramagnetism, and weak Fe-O bonds.

Production Iron(II) nitrate can be produced in multiple ways, such as the reaction of iron metal with cold dilute nitric acid:

3 Fe + 8 HNO3 + 12 H2O → 3 Fe(NO3)2(H2O)6 + 2 NO If this reaction is conducted below -10 °C, nonahydrate is produced. It readily releases water to give the hexahydrate. The above reaction can also co-produce ferric nitrate. Reacting iron(II) sulfate and lead nitrate under dilute ethanol and then evaporating the solution leads to the formation of the green crystals of the hexahydrate. A solution of iron(II) nitrate is produced by the ion-exchange reaction of iron(II) sulfate and barium nitrate, producing a concentration of up to 1.5 M due to the limited solubility of barium nitrate. The solution of the iron(II) nitrate-hydrazine complex is produced by the reaction of hydrazine nitrate and ferric nitrate at 40 °C with copper(II) nitrate as a catalyst:

4 Fe(NO3)3 + N2H5NO3 → 4 Fe(NO3)2 + N2 + 4 HNO3 If the compound is used in situ, the compound is produced by the reaction of iron(II) chloride and calcium nitrate:

FeCl2 + Ca(NO3)2 → Fe(NO3)2 + CaCl2

Reactions The hexahydrate melts at 60 °C and then decomposes at 61 °C into iron(III) oxide rather than iron(II) oxide. A solution of iron(II) nitrate is much more stable, decomposing at 107 °C to iron(III), with the presence of nitric acid lowering the decomposition temperature. Concentrated nitric acid oxidizes iron(II) nitrate into iron(III) nitrate:

3 Fe(NO3)2 + 4 HNO3 → 3 Fe(NO3)3 + NO + 2 H2O

Uses Iron(II) nitrate has no uses, however, there is a potential use for dye removal.

References

Illustrations

Worked examples

Example 1 — a first encounter with Iron(II) nitrate

Start with the simplest possible case. Write down what Iron(II) nitrate 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 Iron(II) nitrate 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 Iron(II) nitrate 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 Iron(II) nitrate

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

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

Frequently asked questions

What is Iron(II) nitrate in simple terms?

Why does Iron(II) nitrate 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 Iron(II) nitrate?

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 Iron(II) nitrate.