CERTIFIED WATER
SPECIALIST CWS
PRACTICE EXAM
Question 1: Which property of water primarily determines whether it is acidic or basic?
Choices:
1) Hardness 2) Turbidity 3) pH 4) Alkalinity
Correct Answer: pH
Explanation: pH expresses hydrogen ion activity and indicates whether water is acidic, neutral, or basic.Page 1
Question 2: A water sample has a pH of 6.0. Compared with pH 7.0 water, its
hydrogen ion concentration is approximately:
Choices:
1) 10 times higher 2) 5 times higher 3) 2 times higher 4) 100 times higher
Correct Answer: 10 times higher
Explanation: The pH scale is logarithmic. A decrease of one pH unit represents about a tenfold increase in hydrogen ion concentration.Question 3: Which constituent is the principal cause of carbonate hardness in many groundwater supplies?
Choices:
1) Sodium chloride 2) Silica only 3) Calcium and magnesium bicarbonates 4) Dissolved oxygen
Correct Answer: Calcium and magnesium bicarbonates
Explanation: Carbonate hardness is primarily associated with calcium and magnesium combined with bicarbonate and carbonate alkalinity.Page 2
Question 4: Hardness is commonly reported as milligrams per liter expressed as:
Choices:
1) SiO2 2) NaCl 3) CaCO3 4) Cl2
Correct Answer: CaCO3
Explanation: Water hardness is conventionally expressed as an equivalent concentration of calcium carbonate, CaCO3.Question 5: One grain per gallon of hardness is approximately equal to:
Choices:
1) 100 mg/L as CaCO3 2) 5.0 mg/L as CaCO3 3) 17.1 mg/L as CaCO3 4) 1.0 mg/L as CaCO3
Correct Answer: 17.1 mg/L as CaCO3
Explanation: One grain per U.S. gallon is approximately 17.1 mg/L as CaCO3.
Page 3