Chapter 15

Acid Any solution with more H 3 O + ions than OH - Electrolytes Taste sour pH less than 7 React with many metals Strong acid-any acid that completely ionizes in water Weak acid-any acid that partially ionizes in water

Bases Any solution with less H 3 O + ions and more OH - ions Electrolytes Feel slippery pH more than 7 Strong base-any acid that completely ionizes in water Weak base-any acid that partially ionizes in water

Bronstad Lowery acids Any substance that is a “proton donor” Proton=H + binds with water to form hydronium (H 3 O + ions) Ex.

Bronstad Lowery acids Any substance that is a “Proton acceptor” Takes a proton from water forming OH - Ex.

Conjugate acids and bases Conjugate acid-acid formed due to accepting a proton Conjugate base-base formed due to losing a proton Amphoteric-describes a substance that can behave like an acid or a base ex. water base acid conjugate acid conjugate base

Self ionization of water Water is constantly ionizing in itself in the following equilibrium reaction The concentration of hydronium ions in neutrally charged water is 1.00x10 -7 M

Self ionization constant of water [H 3 O + ][OH − ] = K eq. K w can be found from the known concentrations of the hydronium and hydroxide ions in pure water. [H 3 O + ][OH − ] = K w = (1.00 × 10 −7 )(1.00 × 10 −7 ) = 1.00 × 10 −14 The concentration of hydronium ions in a solution measures its acidity. The concentration of hydroxide ions in a solution measures its basicity.

Determining [OH − ] or [H 3 O + ] Using K w Sample Problem A What is [OH − ] in a 3.00 × 10 −5 M solution of HCl? Section 2 Acidity, Basicity, and pH Chapter 15

The hydronium ion concentration can be calculated using K w. The concentration of hydronium ions determines the pH of a substance

pH the pH. The letters p and H represent power of hydrogen. pH can be calculated by the following mathematical equation: pH = −log [H 3 O + ] A solution of pH 0 is very acidic. A solution of pH 14 is very alkaline. A solution of pH 7 is neutral

indicators Compounds that reversible change color depending on the pH of the solution or presence of another chemical change

Calculating pH for an Acidic or Basic Solution Sample Problem B What is the pH of (a) a M solution of HNO 3, a strong acid, and (b) a M solution of KOH, a strong base? Section 2 Acidity, Basicity, and pH Chapter 15

neutralization Neutralization reaction Acids react with bases to form water and a salt Acid + base  salt + water Ex. HCl + NaOH  NaCl + H 2 O

Titrations The gradual addition of an acid to a base or base to an acid until it reaches the equivalence point (pH=7) titrant-solution that is added to a solution with an unknown concentration Standard solution- solution with a known concentration An indicator can be used to determine when the solution is no longer acidic or basic which determines when the equivalence point is reached

Selecting an indicator for a titration Transition range The pH range in which an indicator will change color End point Point in a titration when a definite color change occurs A simple equation, given below, relates the amount n (in moles) of a solute to the concentration and volume. n = cV Here c is the concentration (in moles per liter) and V is the volume (in liters) of the solution.

Buffer solutions A solution made from a weak acid and its conjugate base that can neutralize small amounts of acid or base If HX is a weak acid and X − is its conjugate base, then in a buffer solution composed of the two, the following equilibrium is established: