Acids and Bases An Introduction"
Chemistry 2008!
Content Objectives"
•  Chem students wbat identify acids and
bases using their chemical composition
and observable characteristics.!
•  Chem students wbat recognize that acids
are hydrogen-ion donating and bases are
hydrogen-ion accepting solutions. !
•  Chem students wbat predict acid strength
based on trends using the periodic table. !
Language Objectives"
•  You will label acid-base conjugates
in pairs.!
•  You will identify acids as strong or
weak. !
•  You will compose names of acids
and bases from chemical formulas
individually and in pairs.!
Acids"
Characteristics:!
–  Taste bitter/sour!
–  pH range 0-6.9!
–  Neutralizes bases!
–  Corrosive to metals!
–  Releases H+ when reacting with certain metals.!
–  Reacts with Carbonate ions and releases CO2!
–  Written as either H+ or H3O+(hydronium ion)!
Neutralization reactions ALWAYS produce a salt
and water.
HCl + NaOH  NaCl + H2O
H2SO4 + 2NaOH  Na2SO4 + 2H2O
2HNO3 + Mg(OH)2  Mg(NO3)2 + 2H2O
Types of Acids"
•  Arrhenius"
–  Proton donor (H+)!
–  Forms hydonium ions in water
H3O+!
HNO3 + H2O  NO3- + H3O+!
Types of Acids"
Bronsted-Lowry!
–  proton donor!
–  H+ can attach to something
besides H2O!
HA + B --> HB+ + A-!
Acid
Base
!Acid
!Base!
HCl + NH3  NH4+ + Cl-!
Types of Acids"
Lewis
Acid is the electron pair
acceptor
BF3 + F-  + BF4-
How Many Hydrogens?"
Protic≈ # of protons (H+) that
can be donated.
Monoprotic!
•  Donates only one H+!
Diprotic!
•  Can donate 2 H+!
•  H2SO4  H+ + HSO4 –
!HSO4-  H+ + SO4 2-!
HCl  H+ + Cl-!
Triprotic!
•  Can donate 3 H+!
Polyprotic!
•  Donate more than
one H+!
•  H3A(aq) + H2O(l)  H3O+(aq) + H2A−(aq) !
• 
H2A−(aq) + H2O(l)  H3O+(aq) + HA2−(aq) !
• 
HA2−(aq) + H2O(l)  H3O+(aq) + A3−(aq) !
!!
!
!!
Naming Acids"
Binary Acids=!
•  Prefix hydro-, suffix –ic acid!
•  HCl= hydrocholoric acid!
Oxygen containing acids=!
Strong or Weak Acid?"
Strong Acid"
Weak Acid"
H2SO4!
HI!
HBr!
HNO3 !!
HCl!
CH3COOH!
HF!
H2CO3!
H2S!
H3PO4!
•  Strong acids completely
dissociate!
–  HNO3  H+ + NO3-!
•  Weak acids exist in
equilibrium!
–  HF   H+ + F-!
•  STRONG DOES NOT
MEAN THE SAME THING
AS CONCENTRATED!!
Predicting Strong or Weak"
Electronegativity!
•  The higher the
electronegativity=Stronger the
acid (if moving across the
periodic table) !!
Ion Size!
•  Larger ion =Larger surface
area= Stronger acid (if moving
down the periodic table!
Mg + 2HCl  MgCl2 + H2(g)
Zn + 2HCl  ZnCl2 + H2(g)
Mg + H2SO4  MgSO4 + H2(g)
2HC2H3O2 + Na2CO3
2 NaC2H3O2 + H2O + CO2
Bases"
•  Characteristics!
–  Taste bitter!
–  Soapy to the touch!
–  pH range 7.1-14!
–  Neutralizes acids!
–  Denatures proteins!
–  Electrolytes!
–  Written as OH- (hydroxide ion)!
Milk of Magnesia contains
magnesium hydroxide, Mg(OH)2,
which neutralizes stomach acid,
HCl.
2 HCl + Mg(OH)2
MgCl2 + 2 H2O
Types of Bases"
Arrhenius"
•  Substance contains OH-!
•  Dissociate in water!
•  LiOH  Li+ + OH-!
Types of Bases"
Bronsted-Lowry!
•  Base is the proton (H+) acceptor!
NH3 + H+  NH4+!
Types of Bases"
Lewis
Base is the electron pair
donor
F- + BF3  BF4-
Conjugate Acid-Base pairs"
•  Acids give up H+; in theory what is left
could ACCEPT another H+. This makes
it a conjugate base.!
•  Bases accept the H+; in theory what is
left over could DONATE the H+. This
makes it a conjugate acid.!
Examples "
HF + H2O ---> H3O+ + F-!
NH3 + H2O ---> NH4+ + OH-!
Notice water can be either an acid or a base it
just depends on the solute it is reacting with.!
Examples "
Acid and base anhydrides"
Bases form from the left side of the periodic table. !
•  Metal oxides + H2O  base (metal hydroxide)!
MgO + H2O  Mg(OH)2!
•  MgO is a base without water or a basic anhydride!
Acids form from the right side of the periodic table!
•  Nonmetal oxides + H2O  acid!
SO3+ H2O  H2SO4!
SO3 is an acid without water or an acidic anhydride!
ACID ANHYDRIDES ARE THE POLLUTANTS
RESPONSIBLE FOR ACID RAIN!
Sources"
http://en.wikipedia.org/wiki/Gilbert_N._Lewis
http://en.wikipedia.org/wiki/Svante_Arrhenius!
http://dbhs.wvusd.k12.ca.us/webdocs/Gallery/Lowry.GIF!
http://www.chemcool.com/biography/bronsted.htm!
http://www.bbc.co.uk/schools/ks3bitesize/science/
chemistry/acids_bases_1.shtml
http://educ.queensu.ca/~science/main/concept/chem/
c10/c10cdmo3.htm!
Oh and Science Geek and Amendola Too!