chemistry

Sodium oxalate

Sodium oxalate 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 Sodium oxalate rather than just read about it. In short: Sodium oxalate, or disodium oxalate, is a chemical compound with the chemical formula Na2C2O4. It is the sodium salt of oxalic acid.

Key takeaways

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

Reference excerpt

Sodium oxalate, or disodium oxalate, is a chemical compound with the chemical formula Na2C2O4. It is the sodium salt of oxalic acid. It contains sodium cations Na+ and oxalate anions C2O2−4. It is a white, crystalline, odorless solid, that decomposes above its melting point. Sodium oxalate can act as a reducing agent, and it may be used as a primary standard for standardizing potassium permanganate (KMnO4) solutions. The mineral form of sodium oxalate is natroxalate. It is only very rarely found and restricted to extremely sodic conditions of ultra-alkaline pegmatites.

Preparation Sodium oxalate can be prepared through the neutralization of oxalic acid with sodium hydroxide (NaOH) in a 1:2 acid-to-base molar ratio. Evaporation yields the anhydrous oxalate that can be thoroughly dried by heating to between 200 and 250 °C (392 and 482 °F). Half-neutralization can be accomplished with NaOH in a 1:1 ratio which produces NaHC2O4, monobasic sodium oxalate or sodium hydrogenoxalate. Alternatively, it can be produced by decomposing sodium formate by heating it at a temperature exceeding 360 °C (680 °F).

Reactions Sodium oxalate starts to decompose above the melting point of about 250 °C (482 °F) into sodium carbonate and carbon monoxide:

Na2C2O4 → Na2CO3 + CO When heated at between 200 and 525 °C (392 and 977 °F) with vanadium pentoxide in a 1:2 molar ratio, the above reaction is suppressed, yielding instead a sodium vanadium oxibronze with release of carbon dioxide

x Na2C2O4 + 2 V2O5 → 2 NaxV2O5 + 2x CO2 with x increasing up to 1 as the temperature increases. Sodium oxalate is used to standardize potassium permanganate solutions. It is desirable that the temperature of the titration mixture be greater than 60 °C (140 °F) to ensure that all the permanganate added reacts quickly. The kinetics of the reaction are complex, and the manganese(II) ions (Mn2+) formed catalyze the further reaction between permanganate and oxalic acid (formed in situ by the addition of excess sulfuric acid). The final equation is as follows:

5 Na2C2O4 + 2 KMnO4 + 8 H2SO4 → K2SO4 + 5 Na2SO4 + 2 MnSO4 + 10 CO2 + 8 H2O

Biological activity Like several other oxalates, sodium oxalate is toxic to humans. It can cause burning pain in the mouth, throat and stomach, bloody vomiting, headache, muscle cramps, cramps and convulsions, drop in blood pressure, heart failure, shock, coma, and possible death. The median lethal dose (LD50) by ingestion of oxalates is 10–15 g/kg of body weight. Sodium oxalate, like citrates, can also be used to remove calcium ions (Ca2+) from blood plasma. It also prevents blood from clotting. Note that by removing calcium ions from the blood, sodium oxalate can impair brain function, and deposit calcium oxalate in the kidneys.

References

Illustrations

Worked examples

Example 1 — a first encounter with Sodium oxalate

Start with the simplest possible case. Write down what Sodium oxalate 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 Sodium oxalate 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 Sodium oxalate 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 Sodium oxalate

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

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

Frequently asked questions

What is Sodium oxalate in simple terms?

Sodium oxalate, or disodium oxalate, is a chemical compound with the chemical formula Na2C2O4. It is the sodium salt of oxalic acid.

Why does Sodium oxalate 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 Sodium oxalate?

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 Sodium oxalate.