Acids and Bases

Chemistry Joke THE BASE IS UNDER A SALT!

Acids and bases Acids and bases are two classes of chemical compounds that we encounter frequently in everyday living. Vinegar and lemon juice are common acids. Ammonia and bleach are common bases. Acids and bases have opposite properties and the ability to cancel or neutralize each other. Almost all acids begin with H+, and most bases end with OH-.

Properties of acids Taste sour Are strong or weak electrolytes React with bases to form water and salts React with active metals to produce H2 Turn litmus (and cabbage) red Low pH

Naming Acids—a review Anion Ending Example Acid Name -ide Cl-, chloride Hydro-(stem)-ic Hydrochloric acid, HCl -ite SO32-, sulfite (stem)-ous Sulfurous acid, H2SO3 -ate NO3-, nitrate (stem)-ic Nitric acid, HNO3

Properties of bases Taste bitter Are strong or weak electrolytes React with acids to form water and salts Feel slippery Turn litmus (and cabbage) blue High pH

Two Acid/Base Theories Arrhenius Bronsted- Lowry

Arrhenius Simplest definition and most restrictive Acids supply H+ ions Bases supply OH- ions

Bronsted-Lowry Added to Arrhenius definition of bases Acids are proton (H+) donors But… Bases are proton (H+) acceptors Don’t necessarily have to supply OH- NH3 (ammonia) can now be recognized as a base.

Conjugate Acid/base Pairs Bronsted-Lowry also defined conjugate acids and bases. HA + H2O A− + H3O+ HA is an acid. The product A- is its conjugate base. H2O is behaving as a base. The product H3O+ is its conjugate acid. These pairs differ by only one H+. The compound with the extra H+ is the acid.

Self-ionization of water Sometimes when water molecules collide, a hydrogen ion transfers. H20 + H20  H3O+ + OH- Hydronium ion Hydroxide ion Sometimes the self-ionization of water is shown as: H20(l)  H+(aq)+ OH-(aq) H+ and H3O+ are often used interchangeably. Water can act as both an acid and a base, producing both H+ and OH- ions.

Strong acids and Bases Strength in acids and bases does NOT refer to how corrosive or dangerous they are. Strong acids and bases dissociate (break apart) completely in water. At equilibrium, there is no acid or base left that has not ionized (separated into its ions) One of the most corrosive and dangerous acids, HF, is actually a weak acid.

Strong vs. weak http://www.mhhe.com/physsci/chemistry/c hang7/esp/folder_structure/ac/m2/s1/acm2 s1_1.htm

Acid / Base neutralization When an acid reacts with a base, both are neutralized as water and a salt are produced. Predict the products and write the balanced equation for the reaction of sulfuric acid with potassium hydroxide.

Chemistry Joke Q: Why do chemistry professors like to teach about ammonia? A: Because it’s very basic material!