Ch 19.1 Acids and Bases

Def. Acid  Formula starts with a H (HCl, H 2 SO 4 …)  Tastes “sour”  Common in fruits and vegetables  corrosive  Has a pH between 0-6.9

Acid Behavior  Acids are H+ ion donors  They dissociate in an aqueous solution  Dissociation Rx for HCl  aq  HCl H + + Cl -  Are acids molecular or ionic compounds?  Are acids electrolytes?

Naming Acids

Practice HCL CL- ion: -Chloride ion Hydrochloric acid HClO 3 CLO 3 - : Chlorate ion Chloric acid Chloric acid (no Hydro!) HClO 2 CLO 2 - : Chlorite ion Chlorous acid Chlorous acid (no Hydro!)

Organic Acids – Acids of Hydrocarbons  Have a Carboxyl Group – COOH Acetic Acid (Vinegar)  That dissociates into COO - + H + aq aq  CH 3 COOH CH 3 COO - + H +

Acid Formulas Hydrogen Ion is H+ Always add as many Hydrogen ions as needed to neutralize the anion a.1 H + to CL 1- → HCL b.2H + to CO 3 2- → H 2 CO 3 Practice: PO 4 3-, NO 3 -, SO 4 2-

Review Electronegativity  Increases in this direction

Why are acids H+ donors? Example: HCl  Cl is very electronegative, H not: polar molecule (unequal sharing of valence e-) H-Cl = 0.9 δ+ δ- acids are polar!!!! δ+ δ- acids are polar!!!! But - not all molecules containing Hydrogen are acids!!!! Example: CH 4

Warm-up A molecule made from 1 Nitrogen and two Hydrogen can be written in 2 different ways 1.H 3 N 2.NH 3 a)What is the name of each? b)Which one can dissociate? c)What properties can you assign to each based on the formula?

H+ ion and water  H+ reacts with H 2 O to form an  Hydronium ion H 3 O+ H+ + H 2 O → H 3 O +

Bases

B. Def. of a base (adj. basic or alkaline)  Formula ends with -OH  rare in nature/foods  taste bitter  Slippery (harsh cleaners, drain openers)  Corrosive  pH between

Base Behavior  Dissociation into metal cation and hydroxide anion: OH-  A base is a Hydroxide ion donor aq aq  NaOH → Na+ + OH-  Are bases molecular or ionic cpds?  Are bases electrolytes?

Base Names and Formulas  Name: metal name and ‘hydroxide’  NaOH –sodium hydroxide  Write the formula and dissociation Rx of  Calcium Hydroxide  Aluminum Hydroxide  Cesium Hydroxide

Ammonia NH 3  Exceptional base:  Does not directly release OH-  Instead breaks water apart NH 3 + H 2 O → NH OH - NH 4+ Ammonium ion

Water  Water can act as both: acid and base H 2 O → H+ + OH- Acid Base Acid Base

Testing for Acids and Bases  indicator substances that change color  Litmus paper  Commercially available test strips

Warm-up write the dissociation Rx  FormulaNameDissRx  HNO 3  H 2 CO 3  H 2 SO 4  H 3 PO 4   HBr