Chapter 16 Acids and Bases

Characteristics Acids: – Bases: – Change the color of dyes

Characteristics Add acid to water makes water Add base to water makes it more Add acid to base NaOH + HCl  NaCl + H 2 O

Arrhenius Acids – – Bases – –

Bronsted/Lowry Acids – Bases –

Water as a Bronsted/Lowry H 2 O  H + + OH - H + + H 2 O  H 3 O + Hydronium can bond to many other water molecules

Water and Hydronium H 2 O + HCl  H 3 O + + Cl -

Ammonia as a base HCl +NH 3  NH 4 + Cl - H 2 O +NH 3  NH 4 + OH - An acid and a base always work together to transfer protons.

Amphoteric Species A compound that can Water –Base with HCl –Acid with NH 3

Conjugate acids and bases Every acid/base reaction has – –H 2 O +NH 3  NH 4 + OH -

Practice What are the conjugate bases of the following acids? –

Practice What are the conjugate acids of the following bases? –

Strong Acids 100% ionized –Reaction is not reversible –

Strong Bases 100% ionized – CH 3 - is a VERY strong base –No acidity and takes proton from water

Weak Acids Slightly dissociated CH 3 COOH + H 2 O  CH 3 COO - + H 3 O + Scale on page 598, fig 16.4

Generally HX + H 2 O  H 3 O + + X - Equilibrium favors transfer of proton from stronger acid to stronger base

Practice NH OH -  NH 3 + H 2 O –Does the equilibrium lie to the right or left? –Why

Autoionization of water H 2 O + H 2 O  H 3 O + + OH - This is a very fast reaction Only about 1 out of 10 9 water molecules are dissociated at any time

Generally Shown as: H 2 O  H + + OH -

Ion Product H 2 O (l) + H 2 O (l)  H 3 O + (aq) + OH - (aq) K c = But water is a constant so…

MEMORIZE THIS! K c K w = At equilibrium

Practice Remember: at equilibrium Identify the following as acid or base –[H + ] = 1 e –5 –[OH - ] = 3.2 e –9 –[H + ] = 7.1 e –8 –[OH - ] = 4.6 e –3

pH scale Pain to always use exponents Use logarithmic scale to deal with exponent MEMORIZE:

So… If Therefore… the pH of a neutral solution is 7 –(equal amounts of H + and OH - )

Calculations involving pH If given [OH - ] there are two methods to get pH 1.

Calculations involving pH What is pH if [OH - ] = 3.2 e -5 ? 2.

The pH scale If the pH < 7, the solution is acidic If the pH > 7, the solution is basic If the pH = 7, the solution is neutral See fig 16.5 p. 602

Practice Calculate the pH of lemon juice that has a

How do you undo a logarithm? If Then

Practice What is the [H + ] of a solution that has a pH of What is the [OH - ] of each solution?

Practice What is the pH of What is [HNO 3 ] is

Quiz 1.What is the pH of a solution that has [OH - ] = 2.What is the [H + ] of a solution that has a 3.What is the pOH of a solution that has a 4.Identify all of the above as either acid/base

Weak Acids… Write the acid ionization expression for HCHO 2, formic acid, dissolving in water. This is an equilibrium expression. This gets the designation

HCHO 2  H + + CHO 2 - A student prepared a 0.10 M solution of formic acid and measured its pH. At 25 o C, it was found to be Calculate K a ICE BOX!!!

Niacin… A 0.20 M solution of niacin has a pH of what is the K a for niacin? ICE BOX!!!!