Summary of Reactions
Typical characteristics of these reactions are shown below:
- In precipitation reactions, an aqueous salt solution is mixed with
another aqueous salt solution to form a solid precipitate, if one of the resulting salts
is insoluble. If the new salts that can form are soluble, then no reaction occurs.
- In redox, reactions, a pure element is either consumed or formed in
the chemical reaction. This would include all oxidation reactions involving O2.
Both an oxidizing and reducing agent must be present.
- In acid/base reactions, an acid (such as HCl, HF, HNO3, H2SO4)
reacts with a base (such as OH-, H2O). Look for both an acid and
base as reactants.
Use those simple rules to classify simple reactions. Reactions
involving acids can be tricky since their presence as a reactant does not imply that the
reaction is an acid/base reaction, UNLESS A BASE IS PRESENT. This is also true of
bases like OH- which can be a base or a precipitating agent. Tricky examples
that we discussed include:
- H2SO4 (sulfuric acid) acts as an acid when a
base (like H2O or OH- is present)
- H2SO4 (sulfuric acid) acts as a source of ions
in precipitation reactions (i.e. it is a precipitating agent) when it interacts with a
BaCl2 salt solution
- HNO3 (nitric acid) acts as an oxidizing agent when it
interacts with Cu(s) as in Lab 3.
- NaOH acts as a source of OH- ions in precipitation
reactions such as with Cu(NO3)2 in Lab 3.
Similarities in Reactions:
As there is a continuum in bond types, from ionic (no sharing of
electrons to nonpolar covalent with a complete sharing of electrons), there is a continuum
in
- salt solublity - from very soluble to very insoluble. Even for
"insoluble" salts, a very low concentration of dissolved ions are present in
solution (in numbers insufficient to light a light bulb)
- strength of oxidizing/reducing agents - from strong to weak as
measured by standard reduction potentials (discussed next semester)
- strength of acids/bases - from strong to weak as measured by pKa
(discussed next semester)