a). Determine the atomic and equivalent weights of Na+ and Ca2+. A water sample contains 102 mg/l Na+ and 68 mg/l Ca2+; determine the concentrations of both cations in milliequivalents per liter (meq/l). Atomic weight (AW) Na+ = ? g Na+/mole Equivalent weight (EW) Na+ = ? g Na+/eq AW Ca2+ = ? g Ca2+/mole EW Ca2+ = ? g Ca2+/eq 102 mg/l Na+ = ? meq/l Na+ 68 mg/l Ca2+ = ? meq/l Ca2+ b). Determine the molecular weight and equivalent weight of CaCl2. A water sample contains 168 mg/l CaCl2; determine the concentration of CaCl2 in meq/l. Answers: Molecular weight (MW) CaCl2 = ? g CaCl2/mole EW CaCl2 = ? g CaCl2/eq 168 mg/l CaCl2 = ? meq/l CaCl2 c). A water sample has a total hardness of 185 mg/l as CaCO3. Express the hardness in meq/l. Answer: Total Hardness 185 mg/l as CaCO3 = ? meq/l of hardness d). A water sample has a total alkalinity of 225 mg/l as CaCO3. Express the alkalinity in meq/l. Answer: Total Alkalinity 225 mg/l as CaCO3 = ? meq/l of alkalinity
1) Complete the following basic stoichiometry problems, using as references the relevant reading
assignments; (i) Chapter 2 Wastewater Characteristics, Sections 2-1 to 2-6 pp. 57-131, (ii) class
handout “I.C.4. Stoichiometry,” a primary source of stoichiometric data; and (iii)
“HW7_Stoichiometry Tutorial.” The latter two items are located on the Canvas course web site:
a). Determine the atomic and equivalent weights of Na+ and Ca2+. A water sample contains
102 mg/l Na+ and 68 mg/l Ca2+; determine the concentrations of both cations in
milliequivalents per liter (meq/l).
Atomic weight (AW) Na+ = ? g Na+/mole
Equivalent weight (EW) Na+ = ? g Na+/eq
AW Ca2+ = ? g Ca2+/mole
EW Ca2+ = ? g Ca2+/eq
102 mg/l Na+ = ? meq/l Na+
68 mg/l Ca2+ = ? meq/l Ca2+
b). Determine the molecular weight and equivalent weight of CaCl2. A water sample
contains 168 mg/l CaCl2; determine the concentration of CaCl2 in meq/l.
Answers: Molecular weight (MW) CaCl2 = ? g CaCl2/mole
EW CaCl2 = ? g CaCl2/eq
168 mg/l CaCl2 = ? meq/l CaCl2
c). A water sample has a total hardness of 185 mg/l as CaCO3. Express the hardness in
meq/l.
Answer: Total Hardness 185 mg/l as CaCO3 = ? meq/l of hardness
d). A water sample has a total alkalinity of 225 mg/l as CaCO3. Express the alkalinity in
meq/l.
Answer: Total Alkalinity 225 mg/l as CaCO3 = ? meq/l of alkalinity
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