Sulfuric Acid
IMPORTANT PROPERTIES OF SULFURIC ACID. Sulfuric acid ionizes in two steps:
to form a strong acid solution. The ionization is more extensive in a dilute
solution. Most hydronium ions are formed in the first step. Salts formed with the
HSO 4 − (bisulfate ion) are called acid salts; the SO 4 2− (sulfate ion) forms normal
salts.
Sulfuric acid reacts like other acids, as shown below:
Sulfuric acid has other particular characteristics.
As an oxidizing agent:
Cu(s) + 2H 2 SO 4 (aq) (concentrated) → CuSO 4 (aq) + SO 2 (g) + 2H 2 O(l)As a dehydrating agent with carbohydrates:Other Important Compounds of Sulfur
Hydrogen sulfide is a colorless gas having an odor of rotten eggs. It is fairly
soluble in water and is poisonous in rather small concentrations. It can be
prepared by reacting ferrous sulfide with an acid, such as dilute HCl:
FeS(s) + 2HCl(aq) → FeCl 2 (aq) + H 2 S(g)Hydrogen sulfide burns in excess oxygen to form compounds of water and sulfur
dioxide. If insufficient oxygen is available, some free sulfur will form. It is only a
weak acid in a water solution. Hydrogen sulfide is used widely in qualitative
laboratory tests since many metallic sulfides precipitate with recognizable colors.
These sulfides are sometimes used as paint pigments. Some common sulfides and
their colors are:
ZnS—White
CdS—Bright yellow