Ch1: Chemical Concepts

Question 1

Atomic Weight

Answer 1

The average mass of the atoms of an element, relative to the mass of a Carbon-12 atom.

Question 2

Valence

Answer 2

Combining power of an element, relative to that of the Hydrogen atom.

Question 3

Molecular Weight

Answer 3

The sum of the atomic weights of the atoms that constitute a molecule.

Question 4

Mole

Answer 4

The amount of a substance that contains the same number of elementary entities as there are atoms in exactly 12.0 grams of Carbon-12. (Avogadro’s Number)

Question 5

Equivalent Weight

Answer 5

Weight of a compound that contains exactly 1.0 g-atom of available hydrogen or its equivalent. The definition of an “equivalent” depends on the type of reaction being considered.

Question 6

EW = ______

Answer 6

Atomic Weight / z

Or

Molecular weight / z

Question 7

“Z” depends on…

Answer 7

Ion charge, proton transfer, and electron transfer

Question 8

ppm = ____

Answer 8

Mg/L / specific gravity

Question 9

In the water treatment industry, it is common to express calcium, magnesium, hardness, and alkalinity concentrations in terms of…

Answer 9

CaCO3

Question 10

Mg/L of CaCO3 =

Answer 10

(Mg/L of ion) x (50/equivalent wt)

Question 11

meq/L =

Answer 11

(Mg/L) / (eq wt)

Question 12

Molarity (M)

Answer 12

The concentration of a solution in terms of the number of miles of solute per liter of a solution (mol/L)

Question 13

Normality (N)

Answer 13

The concentration of a solution in terms of the number of equivalents of solute per liter of solution (eq/L)

Question 14

N =

Answer 14

zM

Question 15

Ksp =

Answer 15

([C]^c [D]^d ) / ([A]^a [B]^b)

Question 16

Ksp values must be in… (units)

Answer 16

Moles/ L

Question 17

Solubility rules

Answer 17

Solvent in a dilute solution:
conc. = 1.0

Solids: conc. = 1.0

Elements in zero state: conc. = 1.0

Gases: conc. = partial pressure of gas

Question 18

Rate (r) =

Answer 18

-k [A]^a [B]^b

Question 19

Reaction order

Answer 19

Sum of empirically found exponents (can be a whole number or a fraction)

Question 20

Reactions are regulated by…

Answer 20

Temperature and pressure

Question 21

Zero order reaction

Answer 21

dC/dt = -k C^0 = -k

Ct - Co = -kt

Question 22

Buffer solution

Answer 22

A solution that resists large changes in pH when an acid or base is added or when the solution is diluted

Question 23

Low pH (5.5-8.3):
Moderate pH (8.3-10.8):
High pH (>10.8):

Answer 23

Carbonic acid - H2CO3
Bicarbonate ion - HCO3
Carbonate ion - CO3-2

Question 24

Alkalinity

Answer 24

The measure of the capacity of a water to neutralize acids (absorbing H+ ions without a significant change in pH)

Question 25

Hardness

Answer 25

The sum of the polyvalent metallic ions in solution (charge of +2)

Question 26

Line-soda softening

Answer 26

The removal of dissolved minerals (hardness) from a water in order to minimize scale forming tendencies.

Question 27

carbonate hardness (CH)

Answer 27

The portion of the total hardness that is present in the form of bicarbonate salts (with HCO3) and carbonate compounds (with CO3)

Question 28

Non carbonate hardness (NCH)

Answer 28

The portion of the total hardness that is present in the form of non-bicarbonate salts

Question 29

The volume of a sludge consists collectively of...

Answer 29

Dry solids volume and the water volume