Historical figure · Pearson Edexcel International GCSE revision on Incandio

Svante Arrhenius

Whose Thesis Nearly Failed · Chemist · 1859–1927

Who argued in his doctoral thesis that a dissolved salt has already come apart into charged particles before any current reaches it, was given the lowest grade his examiners could award and still pass him, and received the Nobel Prize for the same idea nineteen years later.

Defend these ideas against Arrhenius

Incandio is a free revision platform for the Pearson Edexcel International GCSE, and on it a topic counts as mastered only once you have learned it, proved it in questions, taught it back and defended it against the person with the strongest claim on it. Svante Arrhenius is that person for 4 topics on the course:

• Why Substances Conduct — the Four Structures Compared — Chemistry
• Hydrogen Ions and Neutralisation — Chemistry
• Solubility Rules and Proton Transfer — Chemistry
• Collision Theory — Chemistry

Who was Arrhenius?

Svante Arrhenius was born near Uppsala in 1859 and submitted his doctoral thesis there in 1884. Its subject was the electrical conductivity of solutions, and its central claim was one his examiners found close to absurd. Faraday had supposed that the current passing through a solution tore the dissolved substance into ions; Arrhenius argued that the ions are there beforehand, that a salt dissolving in water spontaneously comes apart into charged particles that move independently of one another, and that this is why a solution begins conducting the instant the electrodes are dipped in rather than after some interval. He supported it with dilution series showing how conductivity varies with concentration. The Uppsala faculty awarded the thesis a fourth class, the lowest grade compatible with passing, which nearly ended his career. Wilhelm Ostwald read it, travelled to Sweden to meet him, and with Jacobus van 't Hoff drew him into the group who were building physical chemistry as a subject; the theory of electrolytic dissociation was accepted within a decade and brought him the Nobel Prize in Chemistry in 1903. From dissociation he drew the definitions that this course still uses: an acid is a substance that produces hydrogen ions in aqueous solution, an alkali produces hydroxide ions, and neutralisation is those two combining to form water — which explains at once why the neutralisation of almost any acid by almost any alkali gives out nearly the same quantity of heat. He worked on much else besides. In 1889 he described how reaction rate varies with temperature, and in 1896 he calculated the effect of atmospheric carbon dioxide on the temperature of the Earth's surface, the first quantitative treatment of what is now called the greenhouse effect.

Major achievements

• Proposed in 1884 that salts dissociate into ions in solution without any current being applied
• Explained the conductivity of electrolyte solutions, and the variation of it with dilution
• Defined an acid as a source of hydrogen ions and an alkali as a source of hydroxide ions
• Explained why the heat of neutralisation is nearly the same for any strong acid and alkali
• Awarded the Nobel Prize in Chemistry in 1903 for the theory of electrolytic dissociation

Life in brief

• 1859 — Born near Uppsala: Son of an estate steward.
• 1884 — The thesis: Ions already apart. Awarded a fourth class.
• 1887 — Acids and alkalis defined: Hydrogen ions and hydroxide ions.
• 1889 — Rate and temperature: How fast a reaction goes as it is heated.
• 1896 — Carbonic acid and the Earth: The first calculation of the warming effect.
• 1903 — The Nobel Prize: For the thesis they nearly failed.
• 1927 — Dies at Stockholm: Dissociation now taught as obvious.

Explore the life of Arrhenius — five chapters

1. A Fourth Class — The thesis that nearly ended a career
2. Ostwald Comes to Sweden — The Ionists, and a subject invented
3. What an Acid Is — Hydrogen ions, hydroxide ions, and one number for neutralisation
4. Why Heating Speeds a Reaction — The activation energy, 1889
5. Carbonic Acid and the Temperature of the Ground — 1896, and a calculation done by hand

Read the five-chapter life of Svante Arrhenius →

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