1.What is the meq/L if my analytical value for Ca+2 is 60.0 mg/L?
Molar mass of Calcium= 40 g/mol , Valency = +2
mEq = (mg X valence)/atomic weight
= ( 60 x 2 ) / 40 = 3 mEq/L
2.What is the mmol/L if my analytical value for Cl- is 87.0 mg/L?
Molar mass of Cl = 35.453 g/mol
To go from mmol/L to mg/L, multiply by the molecular weight.
To go from mg/L to mmol/L, divide by the molecular weight.
87/35.5 = 2.45 mmol/L
3.I am measuring 22.2 mg/L of Si. What is the equivalent concentration of SiO4?
Molar Mass of Si= 28.09 g/mol
22.2 mg/L = 0.0222 g / L
Number of moles = Amount in grams / Molar Mass = 0.0222 / 28.09 = 0.00079 moles /L
Equivalent concentration of SiO4 = Moles of Si x Molar mass of SiO4
= 0.00079 moles/Lx 92.08 g / mol
= 0.073 g/L
4.What is the concentration of Hydronium ions in mg/L for a water sample with a pH of 1?
pH= - log ( H^+ )
1= - log ( H^+)
( H^+ ) = 1.0 x 10^-1 = 0.1 M = 0.1 moles / L
Mass = 0.1 mole x 18 g/mol = 1.8 g = 1800 mg
Final answer= 1800 mg/L
5. I am measuring 136.7 mg/L of Na. What is the equivalent concentration of NaAlSi3O8?
Molar Mass of Na= 23 g/mol
136.7 mg/L = 0.1367 g / L
Number of moles = Amount in grams / Molar Mass = 0.1367 / 23 = 0.00594 moles /L
Equivalent concentration of NaAlSi3O8 = Moles of Na x Molar mass of NaAlSi3O8
= 0.00594 moles/L x 262.2 g / mol
= 1.558 g/L
6. Combining Calcium and Sulfate Ions would make which of the following compounds?
CaSO4
CaS
Ca(SO4)2
CaS2
Ca2SO4
Ca2(SO4)2
Ca3(SO4)2
Ca2(SO4)3
7.An unknown water sample shows a sulfate absorbance of 0.57. What is the sulfate
concentration of the water sample in mg/L?
< 61.0 mg/L
61.0 mg/L
61.5 mg/L
62.0 mg/L
62.5 mg/L
63.0 mg/L
63.5 mg/L
> 63.5 mg/L
Absorbance value= A+B× Sulfate concentration (in mg/L)
8.An analysis of a water sample yields data as shown. What would be the best
hydrochemical classification for the water?
Answer: Sulfate because its concentration is the largest.
Na 335.0 mg/L
K 13.3 mg/L
Ca 52.1 mg/L
Mg 3.0 mg/L
Cl 222.0 mg/L
SO4 490.0 mg/L
HCO3 88.5 mg/L
a.
Sodium and/or Potassium
b.
Calcium
c.
Magnesium
d.
Chloride
e.
Sulfate
f.
Bicarbonate and/or Carbonate