Acids and Bases

Definitions • Arrhenius– Acid is an H+ donor– Base is an OH- donor

• Bronsted-Lowrey– Acid is an H+ donor– Base is an H+ receptor

• Lewis– Acid is an electron pair acceptor– Base is an electron pair donor

pH

• Measures acidity• = -log [H+]• 7 is neutral• Below 7 is acid, above 7 is base• Close to 7 is weaker, farther away from 7 is

stronger• [H+] = inv log (-pH)• pH + pOH = 14

Common names

• Vinegar Acetic acid• Battery acid Sulfuric acid• Muriatic acid HCl• Stomach acid HCl• Aqua regia HCl + HNO3

• Aspirin Acetylsalicylic acid

Normality

• Equivalents / Liter of solution• Typically, M x subscript of H or OH = N• Need to use normality in titration equation

Acid strength

• Refers to percent dissociation• Measured by Ka

Classification

• Oxy acids– H + an oxygen containing polyatomic anion

• Binary acids– H + a monoatomic anion– OR– H+ a non oxygenated polyatomic anion (ie, CN-)

Oxy acids

• To name:– Name the associated polyatomic anion– Replace –ate with –ic acid– Replace –ite with –ous acid

• To write the formula– Replace the –ic with -ate and write the polyatomic

anion OR– Replace the –ous with –ite and write the polyatomic

anion– Balance your charge out with hydrogen

Examples

• HNO3

• H2SO4

• H2CO3

• HNO2

• H3PO4

• H2CrO4

• H2Cr2O7

Binary acids: no oxygen

• To name:– Prefix is hydro– Name anion with –ic acid ending

• To write the formula:– Write the H– Write the anion formula or symbol– Balance you charge with the subscripts if

necessary

Examples

• HCl• HF• H2S

• HCN• HI

Give names or formulas

• HNO3

• HCl• H2SO4

• Carbonic acid• Nitrous acid• Chromic acid• Hydrocyanic acid

Answers

• HNO3 Nitric acid

• HCl Hydrochloric acid• H2SO4 Sulfuric acid

• Carbonic acid H2CO3

• Nitrous acid HNO2

• Chromic acid H2CrO4

• Hydrocyanic acid HCN

pOH and pH

• pH + pOH always equals 14• This is because the autoionization of water

results in a H+ of 1x10-7 and an OH- of 1x10-7

• Example: if the pH = 7.5, what is the pOH?

Answer

• If the pH = 7.5, what is the pOH?

pH + pOH = 147.5 + pOH = 14pOH = 14-7.5

pOH = 6.5

Neutralization

HCl + NaOH NaCl + HOHYou take the H from the acid and combine it

with the OH from the base. That makes water. What’s left is called a salt.

Titration

• NA X VA = NB X VB

Sample problem

• How many mL of 2.0 N HCl are required to neutralize 30 mL of 3.7 N NaOH?

• NA X VA = NB X VB

• (2.0N)(VA) = (3.7N)(30mL)

• Divide both sides by 2.0N• VA = 55.5mL