Fundamental Chemistry and Hydraulics - Mathematics and Statistics for the Environment - page 353

TABLE 14.5
Relative Strengths of Acids in Water

Acid Formula

Perchloric acid HClO 4

Sulfuric acid H2SO 4

Hydrochloric acid HCl

Nitric acid HNO 3

Phosphoric acid H 3 PO 4

Nitrous acid HNO 2

Hydrofluoric acid HF

Acetic acid CH 3 COOH

Carbonic acid H 2 CO 3

Hydrocyanic acid HCN

Boric acid H 3 BO 3

Source: Spellman, F.R., Handbook of Water and
Wastewater Treatment Plant Operations ,
3rd ed., Lewis Publishers, Boca Raton,
FL, 2013.

14.1.2.7.7 Inorganic Matter
Inorganic matter or inorganic compounds are carbon free, not derived from living matter, and easily
dissolved in water; they are of mineral origin. The inorganics include acids, bases, oxides, salts, etc.
Several inorganic components are important in establishing and controlling water quality.

14.1.2.7.8 Acids
An acid is a substance that produces hydrogen ions (H + ) when dissolved in water. Hydrogen ions are
hydrogen atoms that have been stripped of their electrons. A single hydrogen ion is nothing more
than the nucleus of a hydrogen atom. Lemon juice, vinegar, and sour milk are acidic or contain acid.
The common acids used in treating water are hydrochloric acid (HCl), sulfuric acid (H 2 SO 4 ), nitric
acid (HNO 3 ), and carbonic acid (H 2 CO 3 ). Note that in each of these acids hydrogen (H) is one of the
elements. The relative strengths of acids in water, listed in descending order of strength, are shown
in Table 14.5.

14.1.2.7.9 Bases
A base is a substance that produces hydroxide ions (OH - ) when dissolved in water. Lye or common
soap (bitter things) contains bases. Bases used in waterworks operations are calcium hydroxide
(Ca(OH) 2 ), sodium hydroxide (NaOH), and potassium hydroxide (KOH). Note that the hydroxyl
group (OH) is found in all bases. Certain bases also contain metallic substances, such as sodium
(Na), calcium (Ca), magnesium (Mg), and potassium (K). These bases contain the elements that
produce the alkalinity in water.

14.1.2.7.10 Salt s
When acids and bases chemically interact, they neutralize each other. The compound other than
water that forms from the neutralization of acids and bases is a salt. Salts constitute, by far, the larg-
est groups of inorganic compounds. A common salt used in waterworks operations, copper sulfate,
is used to kill algae in water.