Acid-Base Titration and pH 1. What ions are associated with acids? Bases? 2.What mathematical operation is the pH scale based on? 3.What is the pH scale? How does it “work”? 4.Give the 3 ways to classify acids and bases.

The pH Scale Weak acids Strong acids Weak bases Strong bases The pH scale measures the acidity or basicity, i.e., the concentrations of H + ions or OH - ions. Each number represents a tenfold (10x) increase in ion concentration.

Hydronium (H 3 O + ) and Hydroxide (OH - ) ions… … produced by acids and bases in solutions Also produced by self-ionization of water, where 2 molecules of water produce H 3 O + and OH - by moving a proton: H 2 0(l) + H 2 0(l) H (aq) + OH - (aq) Aqueous Solutions and the Concept of pH

Water is a weak electrolyte What does that mean? Measurements show that molar [H ] and [OH - ] = 1.0 x mol/L Product of [H ] and [OH - ] is always constant called the Ionization constant of H 2 0: K w = [H ] [OH - ] = (1.0 x )(1.0 x ) = 1.0 x °C)

The Formula Ionization constant of H 2 0: K w = [H ] [OH - ] K w = the ionization constant of water [H ] = concentration of hydronium [OH - ] = concentration of hydroxide

As temperature increases… The ionization of water increases - explain… What about when we start to manipulate their concentrations? Explain mathematically, as well… When OH - equals H 3 0 +, what type of solution do we have?

Calculating Concentrations of these ions If we know the concentration of one ion, along with Kw, we can determine the concentration of the missing ion

pH Scale Revisited French for “hydrogen power” Indicates [H ] pH = -log [H ]; since this is based on the power of 10, 1.0 x H = pH of 7 (neutral) Likewise, pOH = -log [OH-]; 1.0 x H- has a pOH of Sum of pH and pOh always equals 14, thus: pH + pOH = 14

Do Now Take Quiz – 20 min. Group work with partner (to be turned in)