Problems

1. Convert 10-10 kg to ug using the detailed-step and the short-cut methods.

2. Convert 180 million gallons per day to m /d.

3. In the equation [Co] = IM/[96,494[Co]Qon/(m/2)], the following values for the factors are given: I = 122.84 A, Qo = 378.51 m3/d, n = 0.77, m = 400, and M = 0.90. Calculate the value of [Co] by indirect substitution and by direct substitution.

4. Water containing 3.5 moles of calcium bicarbonate and 2.5 moles of calcium sulfate is softened using lime and soda ash. How many grams of calcium carbonate solids are produced (a) using the method of equivalent masses and (b) using the balanced chemical reaction? Pertinent reactions are as follows:

Ca (HCO3 )2 + Ca (OH )2 — 2CaCO31 + 2H2O CaSO4 + Na2CO3 — CaCO3 + Na2SO4

5. The results of an analysis in a sample of water are shown in the table below. Calculate the equivalent fractions of the respective species.

Ca(HCO3)2 150 Mg(HCO3)2 12.0

Na2SO4 216.0

6. Calcium hydroxy apatite contains the phosphate and hydroxyl groups. Using calcium hydroxide as the precipitant, the chemical reaction is:

Cas(PO4)3OH(S)i ^ 5Ca2+ + 3PO3- + OH- Ksp,apattte = 10-559

Write the molar mass balance for the total molar concentration of the phosphate radical.

7. State the symbol [spPO4ca] in words.

8. The complexation reactions of the calcium ion with the carbonate species, >2-

CaCO3 ^ Ca2+ + CO3-CaHCO+ ^ Ca2+ + HCO-CaOH+ ^ Ca2+ + OH-CaSO3 ^ Ca2++ SO4-

Write the molar mass balance for the total molar concentration of the CO3 radical.

9. The complexation reactions of the calcium ion with the carbonate species, OH- and SO2- are:

CaCO3 ^ Ca2+ + CO2-CaHCO+ ^ Ca2+ + HCO-CaOH+ ^ Ca2+ + OH-CaSO3 ^ Ca2++ SO2-

Write the molar mass balance for the total molar concentration of the SO4 radical.

10. The concentration of Ca(HCO3)2 is 0.74 gmol/L. Convert this concentration to mgeq/L.

11. An ionic charge balance in terms of equivalents for a carbonate system is shown as follows:

Convert the balance in terms of equivalent concentrations.

12. In the coagulation treatment of water using copperas, FeSO4 • 7H2O, the following complex reactions occur.

A molar mass balance on the ferrous iron produces

where [spFeII] is the total molar concentration of all species containing the iron atom.

Express [spFeII] in terms of the concentrations of the ferrous iron, hydrogen ion, and equilibrium constants.

13. A raw water containing 140 mg/L of dissolved solids is subjected to a coagulation treatment using Fe2(SO4)3. For optimum coagulation, the pH should be raised to 8.2. The current acidity is 6.0(10-4) geq/L. After satisfaction of the existing acidity, the amount of base needed to raise the pH has been calculated to be 1.25(10-6) geq/L. Calculate the amount of sodium hydroxide needed.

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