Acids and Bases

Acids Bases
Sour tasting  Ex: acetic acid (vinegar) Bitter  Ex: Soaps (most bases inedible)
React with metal  Ex: Zn in hydrogen lab Don't react with metal
  Feel slippery
Conduct electricity Conduct electricity
Release H+ ions in solutions (actually Hydronium H3O+) Provide or create OH- ions in water.
Neutralize bases Neutralize acids
React with some indicator solutions React with some indicator solutions


Bronsted-Lowry Theory

Acids are proton donors. Bases are proton acceptors.

So... now this might not be totally obvious but....

The weaker the acid, the stronger the conjugate base. If the conjugate base wants H+ more than water wants the H+ then the acid molecule stays together. This is the definition of a weak acid (mostly stays as a molecule)

HA          +         H2O     <===>           H3O+        +             A-

acid                          base                                       C.A.                            C.B.

proton donor           proton acceptor                  where proton ends        acid without proton

Good, high level review. Start with electrolytes and work your way down.

pH Tutorial


Generic Neutralization reaction
acid + base ----> salt + water
HCl + NaOH ----> NaCl + HOH

At Neutralization we know that the strength of the acid times its volume has been exactly matched by the strength of the base times its volume. The strength units must be N (normality) to put everything on even footing. (Many common acids give 2 or even 3 H+ ions per mole, so we can't just use molarity.)

Na x Va = Nb x Vb  at the point of Neutralization.

If you want some online practice, try these. Have a calculator handy.

More than pH

Disassociation of Water

Water: must be present to have either acids or bases.

K(w) = 10
-14 always always always.That means 1 in a hundred trillion molecules of water falls apart, or disassociates into H+ + OH-. This value is a constant at 25 C.

So [H+] x [OH-] = 10
-14 always. So in neutral solutions

[H+] x [OH-} = 10-14 Where are  [H+] and [OH-] equal? 
[10-7] x [10-7] or pH = 7

If one goes up, then the other must go down!

This means that pH+ pOH = 14 always !!!!!

Another result of this is that Ka x Kb = Kw


Given molarity of an acid (concentration of H+):
Want pH :
1) take log of concentration
2) change sign (drop negative)

Given pH:
Want [H+] (the concentration of H+):
1) change sign of pH to negative
2) antilog that negative number:  10-pH

Given pH:
Want pOH:
1) 14-pH = pOH

Given [OH-]:
Want pOH:
1) log of [OH-]
2) change sign (drop negative)

Given pOH:
Want [OH-]:
1) change the sign of pOH
2) antilog that negative number 10 -pOH

pH + pOH = 14 always , pH + pOH = 14 always , pH + pOH = 14 always ,