CIV 340S FINAL EXAMINATION FALL 2017 Name For fuill credir show calculations PAR
ID: 1714188 • Letter: C
Question
CIV 340S FINAL EXAMINATION FALL 2017 Name For fuill credir show calculations PART I1 (OPEN BOOK) 100 pts Useful information: Atomic weight: C-12 g/male;016 g mole: H-1 g/mole; Na- 23 g/mole; S-32 g/mele; CI-35.5 g/mole, K 39 g/molN i I and 1 atm; 1 mole of gas 24.46 , at 25C and I atm; R-0.082056 Latm/K-mol 1 mole of gas 1 (25 pts) Find pH and pOH of a solution coetaining 6.15-10-mmon of H·(please pay attention to units) 2(Q5 ps)jFrtfe OD, Kin hatsrerur i 120 mgl. and the ukiuse BOD is 3s50 mgl, find to) the reaction costant. ob) In what umisExplanation / Answer
1) [H+] = 6.15 x 10-3 mmol/L = 6.15 x 10-3 x 10-3 M = 6.15 x 10-6 M
pH = -log(6.15 x 10-6) = 5.211
pH + pOH = 14
=> pOH = 14 - pH = 14 - 5.211 = 8.789
2) Ultimate BOD (L0) = 350 mg/L
BOD4 = L0 (1 - e-4k) = 120 mg/L , where k is reaction constant
=> 350 x (1 - e-4k) = 120
=> (1 - e-4k) = (120/350)
=> e-4k = 1 - (120/350)
=> -4k = ln(1 - (120/350)) = -0.41985
=> k = 0.105 per day