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cee115-fall99-mt1-Sedlak-soln

cee115-fall99-mt1-Sedlak-soln - CE 115 Water Chemistry Name...

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Unformatted text preview: CE 115: Water Chemistry Name: Midterm Exam 1 Fall 1999 Exam 1 Answer all questions in the space provided. One sheet of notes is allowed. Unless specified otherwise, assume 1 = 1.0, T = 25°C, 1 am. If you are uncertain about the wording of a problem make a reasonable assumption. Write down any assumptions made to solve problems. H20 = H‘ + 0H Kw=10'” Question Score Total l. (30 points total) You are in charge of the disposal of a series of barrels of chemicals at an abandoned industrial site. The first step in your cleanup will be to neutralize the acidic chemicals. You encounter a drum that contains 400L of a solution denoted as “0.5 M H3CCOOH" H3CCOOH = H+ + H3CCOO' I<=1o*-76 (a) Estimate the pH of the solution. £1! 6' - {3:} = {err} , (6‘90? H - L.» a? urcor‘ I J {m} i I I I,” “"1 = “H 41 mum-1 {'7'} (mpg. fut" FW‘“ ,3“, ? [rim '1 flu duet: Wet/nod) new?“ [W]; (6001? luv/(flu, 7604 w - {1'53 nr Int VP feflolflnt _ a :'( '5f I; 3- Vat. b“- t. = 169' V'" and I“ M . C: ~19; {gccwjmriap 0") ("7: awe” Uh" 1.53? (b) What mass of solid NaOH (molecular weight = 40 gfmole) is required to raise the P“ to 40? Flat Wheaten-"'05! full-F. latent; [ugly ear} = [or] 1- [45:50? (”N = 5:? -— (”’1 + EL Mum'er Qol ”'1 Mid: : "" - «m 1271.0 " ’9 ‘0‘ L—f— [9,} [a “fit, ’0 ”‘1‘ My .- 0.579; M amwfiflvflh “Wt-r “1}.— mm}... (5 not; (c) Examine your answer for pan (b). Would your estimate of the mass required be higher or lower if you had not assumed that Y = 1.0? Explain your reasoning. (in neutron} ”H (a? “If". 4 ‘ r. = tx'Jrn'j’In'L- 19'.- k. 1‘5 W qu___ 7.9743' Yam?! (lem) mm}! k.' > K4 runmwmm Mar (5) M“ In 74w rw; waved Fuc- {1M} warme- nun Mars 41.0.4 4‘ (h: run is ran-414' u; grate? (2) (35 points total) SOzm parfitions into cloud droplets according to the following reactions: H20 + song) = st03 K=10°'1 - :- (”£9 ‘ F' H2503 = H” + H803" I<:=10"-a “(TH—l" “,3 F HSOg’ = H‘ + 3032‘ K=10‘9‘° " ["5 i j I ".9 not?) ‘ (a) A rainwater sample collected using an airplane yielded a pH of 4.5 and a total dissolved 50 V) concentration of 10" M. Assuming that the droplet was equilibrated with the surrounding air, estimate the gas phase concentration of SO1 (i.e.. P502). 50.9} -_ {ul5e1]+ (art; 7 J- [5'0 "J 2:031 J {"156}! = ‘33: t (”‘91 - Marat 1:...ng k £8”? [1") (rev): an 020‘}: gait-H an , rm M'J' ( ' V _ r0“ '1 = mil (1 + :9; i Fain) rm (”w Pick : ’0", fl“— &z&"'{n I6” .5- "V" x042) lo—fir (’0‘?!) 1!: [it 1 (.5? U0" iafh = {a'é’i'ar - 0' Mm!) / (b) Assume that the cloud from part (a) intercepts a parcel of air that contains 1045 atm of NH“. Assuming that the cloud does not affect the gas phase concentration of NH3, calculate the pH of the cloud droplet after the droplet reaches equilibrium. (30510” atm) v NH”, = ”Ham K = 10” : (mg—3 ' ‘5’ 5 p NH4+:H*+NH3IU Kzlo-u ' (*m fly [ Uflgfi'} H20 + (201(5) = H2C03* K=10-1.5 H2C03“ = H* + HCOJ- K=10—6.35 HC03' = If + C0," K=10'1°'3 €45. ‘ .- IUM * H“! = ten-14mm + zrro.*'}vH-*10, J + 2m J {W (UM: [gig z Kate,” {:1 -——-.L—-— Kl” tag (”W ‘ tum/3m Iron: tam/«Pm ('71 '“" -.W—.—. U . (““37 ,(sle Tu, flNt':0c.?J flOJL tag {’43} Cr] (1”) '- W i a (“It‘lcrfll Pm- (w ‘ Axruur (KOJ‘Y; (ff), “I; [’4'] a (OH-I (”V 86* 160MB) gm {3“} .. ég:fl:@jma_:’) r 0— "" {lof'yfl’aj'i} (204%) { m) [m I It) ‘TH‘LI =- Io"”'w 4r. MR" (w (H') ' {0‘0”} - t? in in hf“: (3) (35 points total) Alum (AlgSO‘an) and amorphous aluminum hydroxide (Al(Ol-l)3m) are forms of Al[lll] that could be added to water or wastewater to enhance coagulation of particles. A560,)”, = 2 A11“ + 3 so:- + 41 "' Al(OI-I)3(,,+3 H =A1-"' + 3 H10 K=10'” — _{_fi?{ A1(OH)7(77 + 2 H” = Alon“ + 2 H20 K=1053 Ega+ Al(Ol-I)3(_,+ H*=A1(0H); + H20 K=1015 A1(0H)3(,, = Al(0H)3° K=10“3 Al(OH)3(., + 171,0 = ARCH); + H‘ K=10m (a) Calculate the final concentration of dissolved A10”) in a solution in equilibrium with ARCH)”, at pH=8. [41:21»)?- [11“] MIN"! HHWJIMAHMH (#1555071 no»; 7 k («*1 7 k («*1 2 t7 * (:7: ,7 7. 7-“) «MW» va'wxo'“) (7r ‘ 20* '9 *0” 1’ ( m (7% “1-.th ‘1'- --fi l..- 0*“: =Is"7ro rm '10 (MW!) ‘ 1.2?w0'7fl (b) The solution from pan (a) is filtered to remove the Al(OH)3(,,. Calculate the alkalinity of the water. - u':.r...i_, 7 41! 7mm our ”suing/7H h“ 477.777."; Hie-Ha. €77 «(4" r70 Cpfitqs) C;“"'”" J77” [flan‘v- {#1 "J ’ ion-v kg? I 0111- =3) ,2 .. 4w {ye-(tn Hr:0rndvrr AU AU = {Ml 2 Emery 4o2[At(wy‘*} 2 HAIIMA 7 HUI/ng :- IO" 4 10"”: 200“ Jeff“? Y'f + 9'60 Y7{‘9-$j '* VHHWO'VM (0) Discuss in a qualitative sense the effect of addition of alum and amorphous aluminum hydroxide on the alkalinity and pH of water or wastewater. In other words, how will alum or aluminum hydroxide affect alkalinity and pH? Consider water or wastewater with a pH between 6 and 8 all»: - flit-gadifl} Q'SWVH '0 594 21'! "r 359?.- mnnuc Mira: m 5'0," (”de 1“” (“W‘c’lm) ,3!” Mandy its 10 Fun 4901‘”, Mpfifielc 7&7: ”MW! efu‘ FdOM In: yawn [ a) creme wand} 11!“ rdLo —) #104” J. .41" Thu-r6»: .- f H J with. 141%)” em; a/hfrwly ‘5‘» Untim-Jtl Emma, {ML 0" fluid Ufl B1 Ill gutrph a. (#5,, “(u-HR AIMIUNU' WLH- MN“! “b WG-‘fv 0/ mike/rkr ’7 57”” ANNA .07ch 4‘ WWW?“ I! 5,,th pH .1, u: A! [it’d/Irv .g 16/an pill #:54qu ” A1/W}*:/JUM/:M“ [If 4* PM“ Fe” (a; we M (Lin! pH .5 IF éflfflflzg Ar If; :4 _ ”I 4100f =(:0”j(l¢? 5) = :0 ' Mfafl,‘ z 10"” - I04" _I—'J'H.f ...
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