Svante Arrhenius was a Swedish chemist and physicist whose ideas changed how scientists understand solutions, acids, bases, and reaction rates. In the late 1800s, he proposed that some substances separate into charged particles called ions when dissolved in water. This explained why salt water conducts electricity and why acids and bases behave in predictable ways.
His work helped build the foundation of modern physical chemistry and earned him the 1903 Nobel Prize in Chemistry.
Arrhenius is best known in chemistry for ionic dissociation theory, the Arrhenius definitions of acids and bases, and the Arrhenius equation for reaction rates. His acid base model says acids produce H+ in water, while bases produce OH- in water. He also connected temperature to chemical reaction speed with the equation k = A e^(-Ea/RT), which is still used in kinetics.
Beyond chemistry, Arrhenius made an early quantitative prediction that increasing atmospheric CO2 could warm Earth, making him an important figure in the history of climate science.
Key Facts
- Arrhenius acid: a substance that increases H+ concentration in water.
- Arrhenius base: a substance that increases OH- concentration in water.
- Ionic dissociation means compounds separate into ions in solution, such as NaCl(aq) -> Na+(aq) + Cl-(aq).
- Neutralization can be summarized as H+(aq) + OH-(aq) -> H2O(l).
- Arrhenius equation: k = A e^(-Ea/RT), where k is the rate constant and Ea is activation energy.
- Svante Arrhenius received the 1903 Nobel Prize in Chemistry for his work on electrolytic dissociation.
Vocabulary
- Ionic dissociation
- The separation of a dissolved compound into positive and negative ions in solution.
- Electrolyte
- A substance that forms ions in solution and allows the solution to conduct electric current.
- Arrhenius acid
- A substance that produces hydrogen ions, H+, when dissolved in water.
- Arrhenius base
- A substance that produces hydroxide ions, OH-, when dissolved in water.
- Activation energy
- The minimum energy particles need to react successfully during a collision.
Common Mistakes to Avoid
- Calling every hydrogen-containing compound an Arrhenius acid is wrong because the compound must increase H+ concentration in water.
- Calling every OH-containing compound an Arrhenius base is wrong because the substance must release or produce OH- ions in aqueous solution.
- Forgetting charges when writing dissociation equations is wrong because ions must show both correct formulas and correct electrical charges.
- Assuming a higher activation energy makes a reaction faster is wrong because larger Ea usually lowers the rate constant at the same temperature.
Practice Questions
- 1 Write the dissociation equation for calcium chloride in water, CaCl2(aq), and state how many moles of ions form from 1.0 mol of CaCl2.
- 2 A reaction has A = 2.0 x 10^12 s^-1, Ea = 50,000 J/mol, R = 8.314 J/(mol K), and T = 300 K. Use k = A e^(-Ea/RT) to estimate the rate constant k.
- 3 Explain why HCl(aq) is an Arrhenius acid but methane, CH4, is not, even though both compounds contain hydrogen.