8.3 STRONG AND WEAK ACIDS AND BASES
DEFINITIONS:
ELECTROLYTE: any substance that dissolves in water to produce ___________ (and hence conduct
_________________ (may be acids, bases or salts)
 STRONG ACIDS/BASES/ELECTROLYTES: dissociate __________________ into ions
WEAK ACIDS/BASES/ELECTROLYTES: dissociate _________________into ions; (usually less than____%).
SOME EXAMPLES OF STRONG & WEAK ACIDS:
STRONG NAME
ACIDS
*H2SO4(aq)
diprotic
WEAK
ACIDS
*HCOOH(aq)
*HNO3(aq)
monoprotic
*CH3COOH(aq)
*HCl(aq)
monoprotic
*C2H5COOH(aq)
HBr(aq)
monoprotic
NAME
*H2CO3(aq)
(diprotic)
HI(aq)
monoprotic
H3PO4(aq)
(triprotic)
HClO3(aq)
monoprotic
H2S(aq)
(diprotic)
*IB requires you to memorize the entities with an ASTERISK BEFORE IT ONLY!
*NOTE: There are ONLY_____ strong acids….if it’s not one of these 6, the acid is ____________.
*The first 3 Weak acids listed are example of ____________________ acids. They are all monoprotic. We will study
these in more detail when we get to organic chemistry.
ACTIVITY:
a) Illustrate the “diprotic nature” of sulfuric acid:
b) Illustrate the monoprotic nature of ethanoic acid:
*Use a ______________arrow to represent _____% dissociation; a _____________ acid or base.
*Use _____________ arrows to represent ______________dissociation; a ___________ acid or base.
VIEW THE FOLLOWING WEB ANIMATION - Weak vs. Strong Acids:
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/acid13.swf
Strong Acids
Weak Acids
*DEMONTRATION: Conductivity (Weak versus Strong Acid)
ACID
CONDUCT?
EXPLANATION
HCl(aq)
WEAK OR STRONG?
CH3COOH(aq)
*COMMON MISCONCEPTION:
Don’t confuse _______________________ with __________________.
CONCENTRATION = ______________ to _______________ ratio [can be changed by adding _____________ (i.e.
diluting)]
STRENGTH = “strong” and “weak” are _______________________ of acids and bases that ______________ be
changed (e.g. cannot “weaken” a substance by adding water)
ACID
HCl(aq)
CATEGORY
_____ mol dm
DILUTE
_____ mol dm-3
_____ mol dm-3
_____ mol dm-3
CONCENTRATED
-3
CH3COOH(aq)
DISTINGUISHING BETWEEN STRONG AND WEAK ACIDS:
TEST
Add reactive metal e.g. Mg
STRONG ACID
__________ H2 production
WEAK ACID
__________ H2 production
Add a carbonate, CO32-
__________ CO2 production
__________ CO2 production
Conductivity
_______ (many _______)
________ (few ______)
pH of 0.1 M solution
=1
=3-4
EXTENSION: Draw Lewis structures for nitric, phosphoric and sulfuric acids:
SOME EXAMPLES OF STRONG & WEAK BASES:
STRONG
BASES
*LiOH
NAME
WEAK
BASES
*NH3
*NaOH
*CH3NH2
*KOH
*C2H5NH2
*Ba(OH)2
*C3H7NH2
NAME
*Group ___ & ____ hydroxides = _____________ bases.
*The last 3 weak bases listed are examples of _______________. Again, we will study these in more detail when we
get to organic chemistry.
*ACTIVITY:
a) Write dissociation equations for sodium hydroxide and barium hydroxide.
b) Write dissociation equations for ammonia and aminomethane.