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 + HNO 3 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 HNO 3 H 2 SO 4 H 2 CO 3 HNO 2 H 3 PO 4 H 2 CrO 4 H 2 Cr 2 O 7

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 H 2 S HCN HI

Give names or formulas HNO 3 HCl H 2 SO 4 Carbonic acid Nitrous acid Chromic acid Hydrocyanic acid

Answers HNO 3 Nitric acid HClHydrochloric acid H 2 SO 4 Sulfuric acid Carbonic acidH 2 CO 3 Nitrous acidHNO 2 Chromic acidH 2 CrO 4 Hydrocyanic acidHCN

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 = pOH = 14 pOH = pOH = 6.5

Neutralization HCl + NaOH  NaCl + HOH You 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 N A X V A = N B X V B

Sample problem How many mL of 2.0 N HCl are required to neutralize 30 mL of 3.7 N NaOH? N A X V A = N B X V B (2.0N)(V A ) = (3.7N)(30mL) Divide both sides by 2.0N V A = 55.5mL