Acid and Bases

Common Household Items

Properties of Acids Acid solutions conduct electricity well Acids react with many metals Sour taste (lemon) Generate hydronium ions (H3O) pH is less than 7 Many acids are liquids or gases

Properties of Bases Also an electrolyte Many bases are solids Slippery to touch Generate hydroxide ions (OH-) pH of 8 or higher

Definition of an Acid Bronsted-Lowry acid: a substance that donate a proton to another substance HCl + H2O  H3O + Cl

Definition of a base Bronsted-Lowry base: a substance that accepts a proton NH3 + H20  NH4 + OH

Kw Water can act both as an acid and a base The self-ionization constant of water is when the products of the concentrations of the two ions that are in equilibrium with water; [H3O +][OH-] Kw = 1.00 x 10 -14 Kw is always a constant. Anything that increases one ion concentration, will decrease the other ion concentration.

Meaning of pH pH is a value used to express the acidity or alkalinity of a solution. pH below 7 is acidic pH of 7 is neutral pH above 7 is basic

Calculations pH = - log [H3O+] [H3O+] = 10-pH Solution of pH = 0 is very acidic! Solution of pH = 14 is very basic Refer to p. 543 for calculator help

calculations pH = -log [H3O] Take the logarithium of the [H3O] and change the sign to negative. [H3O] = 10 –pH Change the sign of the pH Use the antilog to raise the 10.

Calculations What is the pH of a 0.00010 M of HNO3? pH = -log (1.0 x 10 -4) = -(-4.00) = 4.00 What is the pH of a 0.0136 M solution of KOH? You must use Kw. [H30] = kw = (1.0 x 10 -14) = 7.35 x 10 -13 [OH] (1.36 x 10 -2) Then pH = - log (7.35 x 10 -13) = 12.13

Calculations What are the hydronium and hydroxide ions in a sample of rain that has a pH of 5.05? [H3O] = 10 –5.05 = 8.9 x 10-6 M [OH] = Kw = 1.00 x 10-14 [H3O] 8.9 x 10-6 = 1.1 x 10-9 M