1. CE 441 - ENVIRONMENTAL ENGINEERING
Midterm #1 Study Guide
The following information will be given in solving the problems:
H2CO3 ↔ H+ + HCO3
Ka1 = 5.0 x 10-7 M @ 25oC
HCO3 ↔ H+ + CO3=
Ka2 = 5.0 x 10-11 M @ 25oC
+
H2O ↔ H + OH
Kw = 10-14 M @ 25oC
Alkalinity = [HCO3-] + [CO3=] + [OH-] - [H+] (all concentrations expressed as CaCO3)
BODt = BODultimate(1 - e-kt)
KT = K20(θ)T-20
For a batch reactor and 1st order reaction: Ct/Co = e-kt; t1/2 = ln2/k = 0.693/k
Mass loading rate (lb/day) = Q (in MGD) x C (in mg/L) x 8.34
1 ft3 = 7.48 gal, 1 gal = 3.785 liters, 1 m3 = 35.3 ft3
Atomic weight: H =1, C =12, N = 14, O =16, Na = 23, Mg = 24, Al = 27, P =31, S =32, Ca = 40,
Fe = 56, Cl = 35.5
I. True or False (1 pt each, 18 pts total):
1. ___ The unit of the rate constant of a first-order reaction (dC/dt = -kC) is unitless.
II. Fill the Blanks (1 pts each, 10 pts total):
1. MCL (for potable water) = Maximum ______________________________________ level.
III. Short answers (4 pts each, 12 pts total):
1. Write down the general equation describing change in concentration relative to time.
IV. Calculation problems (Show your calculations; 5 pts each, 60 pts. total)
1. If 98 mg of sulfuric acid (H2SO4) is added to two liters of water at 25 oC, what is the final pH?
[Note: Sulfuric acid is a strong acid and H2SO4 → 2H+ + SO4=]
pH = ________________
2. A water sample contains 10-4 M HCO3- at pH = 7, estimate the H2CO3 concentration.
[H2CO3] = _______________M
3. The results of a well water analysis are given as:
Na+ = 60 mg/L, Ca++ = 165 mg/L, Mg++ = 15 mg/L, HCO3- = 122 mg/L, CO3= = 20 mg/L, SO4= =
50 mg/L, Cl- = 30 mg/L.
Total alkalinity ≈ __________ mg/L as CaCO3.
1
![CE 441 - ENVIRONMENTAL ENGINEERING
Midterm #1 Study Guide
The following information will be given in solving the problems:
H2CO3 ↔ H+ + HCO3
Ka1 = 5.0 x 10-7 M @ 25oC
HCO3 ↔ H+ + CO3=
Ka2 = 5.0 x 10-11 M @ 25oC
+
H2O ↔ H + OH
Kw = 10-14 M @ 25oC
Alkalinity = [HCO3-] + [CO3=] + [OH-] - [H+] (all concentrations expressed as CaCO3)
BODt = BODultimate(1 - e-kt)
KT = K20(θ)T-20
For a batch reactor and 1st order reaction: Ct/Co = e-kt; t1/2 = ln2/k = 0.693/k
Mass loading rate (lb/day) = Q (in MGD) x C (in mg/L) x 8.34
1 ft3 = 7.48 gal, 1 gal = 3.785 liters, 1 m3 = 35.3 ft3
Atomic weight: H =1, C =12, N = 14, O =16, Na = 23, Mg = 24, Al = 27, P =31, S =32, Ca = 40,
Fe = 56, Cl = 35.5
I. True or False (1 pt each, 18 pts total):
1. ___ The unit of the rate constant of a first-order reaction (dC/dt = -kC) is unitless.
II. Fill the Blanks (1 pts each, 10 pts total):
1. MCL (for potable water) = Maximum ______________________________________ level.
III. Short answers (4 pts each, 12 pts total):
1. Write down the general equation describing change in concentration relative to time.
IV. Calculation problems (Show your calculations; 5 pts each, 60 pts. total)
1. If 98 mg of sulfuric acid (H2SO4) is added to two liters of water at 25 oC, what is the final pH?
[Note: Sulfuric acid is a strong acid and H2SO4 → 2H+ + SO4=]
pH = ________________
2. A water sample contains 10-4 M HCO3- at pH = 7, estimate the H2CO3 concentration.
[H2CO3] = _______________M
3. The results of a well water analysis are given as:
Na+ = 60 mg/L, Ca++ = 165 mg/L, Mg++ = 15 mg/L, HCO3- = 122 mg/L, CO3= = 20 mg/L, SO4= =
50 mg/L, Cl- = 30 mg/L.
Total alkalinity ≈ __________ mg/L as CaCO3.
1](https://image.slidesharecdn.com/midterm1studyguide-140206222516-phpapp02/85/midterm-1-study-guide-1-320.jpg)
