Question 1: Name two properties of an acid- Question 2:Name two properties of a base? Academic Chemistry March 20,2012 sour, corrosive, reacts with metals to produce hydrogen gas, turns blue litmus paper red. Bitter, slippery, turns red litmus paper blue

Section 20.2 Self-ionization of water:  Reaction in which 2 water molecules produce ions  H 2 O + H 2 O → OH - + H 3 O +  Also written as: H 2 O ↔ H + + OH -  The H 3 O + and H + represent hydrogen ions in solution.

Neutral Solutions In pure water, the concentration of hydrogen ions is equal to the concentration of hydroxide ions  1 x M Remember M represents Molarity  [H + ] = [OH - ] (brackets represent concentration)  The represents a neutral solution.

NUMBER LINE Remember the number line Which is greater? 0 or 3 33 Which is greater? -7 or -4  -4 Which is less? -2 or -4  Increasing

Solutions In a solution, if the [H + ] increases, the [OH - ] decreases and vice versa.  Think back to our see-saw. As one person went up the other went down. Ion-product constant of water, Kw:  Kw = [H + ] x [OH - ] = 1 x M Acidic Solution:  The [H + ] is greater then [OH - ].  Therefore, the [H + ] is greater then 1 x M. Think about the # line. -5 is GREATER than -7 Basic Solution:  The [H + ] is less than [OH - ].  Therefore, the [H + ] is less than 1 x M.  A.k.a. alkaline solutions

Problem If the [H + ] is 1 x M, is the solution acidic, basic, or neutral? What is the [OH - ]? Acidic [OH-] = 1x /1x10 -5 = 1x10 -9 M

Problem If the [H + ] is 1 x M, is the solution acidic, basic, or neutral? What is the [OH - ]? Acidic [OH-] = 1x /1x10 -3 = 1x M

Problem If the [H + ] is 1 x M, is the solution acidic, basic, or neutral? What is the [OH - ]? Basic [OH-] = 1x /1x = 1x10 -3 M

pH Scale The pH scale ranges from  0 = strongly acidic  7 = neutral  14 = strongly basic pH = -log [H + ] What is the pH of a neutral solution?  Log is a function on the calculator

Sample Problems What is the pH of the following concentrations?  [H + ] = 1 x M  [H + ] = 1 x M  [H + ] = 1 x M As long as you have a 1 x 10 to some power, the pH is the exponent.

Sample Problems If you do not have 1 to the power then you MUST use our formulas. What is the pH of the following?  [H + ] = 2x10 -2 pH = -log(2x10 -2 ) = 1.7  [H + ] = 6x10 -9 pH = -log(6x10 -9 ) = 8.2  [H + ] = 3x10 -5 pH = -log(3x10 -5 ) = 4.5

Other Formulas and Problems pOH = -log [OH - ] [OH - ] = 10 -pOH pH + pOH = 14 Kw = [OH - ] x [H + ] = 1x10 -14

Other Formulas and Problems What is the pH of a solution with a [OH - ] of 4.0 x M?  Two ways to solve: 1. find pOH then subtract from 14  pOH = -log[OH-] = 10.4  = 3.6

Other Formulas and Problems What is the pH of a solution with a [OH - ] of 4.0 x M?  Two ways to solve: 2. Use Kw to find [H + ] then find pH using –log function.  Kw = [OH - ] x [H + ] = 1x  [H+] = 1x /4x = 2.5x10 -4  -log(2.5x10 -4 ) = 3.6

Flow Chart of pH and pOH Use the map to help you get from any point A to any point B…

More Samples What is the [H + ] of a solution with a pH of 3.7?  [H+] = = 2.0x10 -4 What is the pOH?  = 10.3 What is the [OH-]  [OH-] = = 5.0x10 -11

More Samples If the [H + ] is 3.1 x M, what is the pH?  pH = -log(3.1x10 -5 ) = 4.5 What is the pOH?  = 9.5 What is the [OH - ]?  [OH - ] = = 3.16x10 -10

CLASS/HOMEWORK Your homework is to do the worksheet provided. It is due on Wednesday at the BEGINNING of class Do not forget the QUIZ TOMORROW!