Overview
This lecture introduces acid-base chemistry, focusing on definitions, reactions, and real-world effects such as acid rain and limestone deterioration, with practical stoichiometric calculations.
Dangers and Importance of Chemistry
- Chemistry labs can be dangerous, with risks including cancer and fatal accidents.
- Despite hazards, chemists have greatly increased human lifespan.
Introduction to Acid-Base Reactions
- Lecture shifts focus from mixing solutions to chemical reactions that transform substances.
- Acid-base reactions are among three major types of solution reactions.
Real-World Acid-Base Reactions: Acid Rain
- Sulfuric acid from coal burning causes acid rain, damaging limestone statues and ecosystems.
- Sulfur in coal burns to form sulfur dioxide, which reacts with water in the atmosphere to create sulfuric acid.
- Acid rain acidifies water supplies and damages materials like limestone, affecting wildlife and infrastructure.
Definitions: Acids, Bases, and Bronsted-Lowry Theory
- Acids taste sour and dissolve substances; bases taste bitter and feel slippery.
- Bronsted-Lowry definition (1923): acids donate protons (H+), bases accept protons.
- In water, acid donates a proton to H2O, forming hydronium ion (H3O+).
- The shorthand “H+ in solution” actually refers to H3O+.
Conjugate Acids and Bases
- Every acid forms a conjugate base after donating a proton; every base forms a conjugate acid after accepting a proton.
- Strong acids have weak conjugate bases and vice versa.
- Water can act as both an acid and a base.
Stoichiometry of Acid-Base Reactions
- Example calculation: burning one ton of coal (3% sulfur) can dissolve about 94 kg of limestone via sulfuric acid formation.
- Acid reacts with calcium carbonate (limestone), producing gypsum (CaSO4), CO2, and water.
Environmental Solutions and Industrial Chemistry
- Limestone scrubbers in power plants neutralize sulfuric acid by converting SO2 to calcium sulfate.
- Flue gas desulfurization removes about 95% of sulfur emissions in U.S. power plants.
- Some captured SO2 is converted into useful chemicals like industrial sulfuric acid.
Key Terms & Definitions
- Acid — substance that donates a proton (H+) in a reaction.
- Base — substance that accepts a proton (H+) in a reaction.
- Hydronium ion (H3O+) — water molecule with an extra proton; actual form of H+ in aqueous solution.
- Conjugate acid/base — product formed when a base accepts or when an acid donates a proton.
- Stoichiometry — calculation of reactants and products in chemical reactions.
Action Items / Next Steps
- Extra credit: Calculate tons of limestone needed to scrub all sulfur from 1 billion tons of 3% sulfur coal.
- Review acid-base definitions and stoichiometry for upcoming lessons.