Chemistry

Lecture 10 Acid & Base

M. Adam Adman

Objec=ves:

Proper=es Defini=ons Strong vs. weak acids/bases Titra=ons

Acid & Base

hLp://www.youtube.com/watch?v=DQk7f6DksN8

hLp://www.youtube.com/watch?v=tNvP3-174_M

hLp://www.youtube.com/watch?v=VX6fazASd7w

acids Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion aLached to a water molecule)

Taste sour Corrode metals Electrolytes React with bases to form a salt and water pH is less than 7 Turns blue litmus paper to red Blue to Red A-CID

Base

Produce OH- ions in water Taste biLer, chalky Are electrolytes Feel soapy, slippery React with acids to form salts and water pH greater than 7 Turns red litmus paper to blue Basic Blue

Defini=ons:

Defini=on #1: Arrhenius (tradi=onal)

Acids produce H+ ions (or hydronium ions H3O+)

Bases produce OH- ions

Defini=on #2: Brnsted Lowry

Acids proton donor

Bases proton acceptor

Defini&on #3 Lewis Lewis acid - a substance that accepts an electron pair

Lewis base - a substance that donates an electron pair

Strong vs. Weak

The strength of an acid (or base) is determined by the amount of IONIZATION.

Strong acids

Hydrochloric acid, HCL Nitric acid, HNO3 Sulfuric acid, H2SO4

Weak acids

Weak acids are much less than 100% ionized in water.

Ex: ace=c acid = CH3CO2H

Strong base

Other Ex: KOH Ca(OH)2

} 100% dissociated in water. NaOH (aq) ---> Na+ (aq) + OH- (aq)

Weak base

Less than 100% ionized in water Ex: Ammonia

ACID-BASE REACTIONS Titrations

H2C2O4(aq) + 2 NaOH(aq) ---> acid base Na2C2O4(aq) + 2 H2O(liq)

Carry out this reac=on using a TITRATION. Oxalic acid,

H2C2O4

Setup for =tra=ng an acid with a base

Titra=on

1. Add solu=on from the buret. 2. Reagent (base) reacts with

compound (acid) in solu=on in the flask.

3. Indicator shows when exact stoichiometric reac=on has occurred. (Acid = Base)

This is called NEUTRALIZATION.

Reference:

Raymond Chang. General Chemistry-the essen=al concepts, 5th ed., McGraw-Hill.

Tutorial 10

Please give 1 example: Strong acid Weak acid Strong base Weak base