Chemical Characteristics of Water Flashcards
(32 cards)
What are the four main sources for inorganic and organic species?
1) Contact of water with minerals, rocks, and soils
2) Rain in contact with the atmosphere
3) Decomposition of organic matter in the environment
4) Municipal, industrial, agricultural and human activities
What are the main inorganic constituents?
Cations: calcium, magnesium, sodium, potassium (Ca2+, Mg2+, Na+, K+)
Anions: carbonate, bicarbonate, sulphate, chloride, nitrate (CO32-, HCO3-, SO42-, Cl-, NO3-)
What causes hardwater?
Calcium and Magnesium (Ca2+ and Mg2+)
What is the typical order for arranging cations and anions in the meq/L graphical representation of possible pairs?
Cations: Ca2+, Mg2+, Na+, K+, anything else
Anions: HCO3-, SO42-, Cl-, anything else
What is the point of the graphical representation of pairs?
To make sure the sum of meq/L of cations is equal to that of the anions
What happens to inorganic compounds in water?
They dissociate into ions
What are the 3 inorganic constituent indicators?
pH
Alkalinity
Hardness
What is alkalinity?
A measure of water’s capacity to neutralize acids (ability to absorb H+ without significant pH change)
What are the major contributors to alkalinity?
Bicarbonate, carbonate, and hydroxide
What are the typical units of alkalinity?
meq/L
mg/L as CaCO3
What is the typical pH value for phenolphthalein alkalinity?
8.3
A pH value below 8.3 usually means there is no carbonate present as it has been converted to bicarbonate, true or false?
True
A pH value below 4.5 usually means there is no bicarbonate present as it has been converted to carbonic acid, true or false?
True
Hardness is cause by what?
Multivalent Cations
(mainly calcium and magnesium in natural waters)
What would happen if you tried to wash dishes with hard water and soap?
The hard water would reduce the soaps cleaning action
What is the most common and troublesome form of hardness?
Calcium Bicarbonate (Ca(HCO3)2
It is picked up by rain water passing through limestone
What is total hardness?
The combination of calcium and magnesium hardness
What are the units of hardness?
mg/L of CaCO3
What ions mainly contribute to temporary hardness?
Bicarbonate and Carbonate
(HCO3- and CO32-)
What is carbonate hardness?
The combination of bicarbonate and carbonate hardness
(also known as temporary hardness)
What ions mainly contribute to permanent hardness?
Chloride and Sulfate
(Cl- and SO42-)
What is non-carbonate hardness?
The combination of chloride and sulfate hardness
(also known as permanent hardness)
What is carbonate hardness typically equal to?
Alkalinity
(or the concentration of bicarbonate in mg/L as CaCO3)
Give the range in mg/L as CaCO3 for the following degrees of hardness:
Soft
Moderately Hard
Hard
Very Hard
0-50
50-150
150-300
300+
