Chemistry QAs (C117)

NATS 1750 A (Fall 2016): Assig nm en t 2, Ve rs io n 1 .0 - D ecem ber 2 1, 2 016 Due: January 31, 2017 by 1 1 p m ED T v ia Mo odle (Late Penalty: 25% per da y - in cl udin g w eeke nds. St rict ly enfo rce d.) Instructions: ● You are expected to p ro vide a nsw ers fo r eve ry q uest io n. Y ou a re e nco ura ged to sh ow all of your work so th at ma rks can b e a w ard ed fo r part ia lly co rre ct a nsw ers.

● Although you are enco ura ged to co lla bora te w it h yo ur cl assm ate s, e ach o f yo u is expected to submit a se para te a nd d ist in ct a ssi gnme nt - a p oin t th at w ill r e quir e acknowledgement u pon su bmi ssi on.

Earth’s present atmosphe re is th eorize d to h ave e vo lve d fro m one b ase d u pon o utg assi ng o f the planet’s interior. Consider that period in E art h’s hist ory when o utg asse d w ate r va pour h as co ndense d to fo rm a significant ocean. During th is sa me p erio d, su ppose th at th ere a re o nly tw o m ech anism s fo r removing CO 2 from Earth’s atmo sphere - name ly photo syn th esi s and d isso lu tio n. ( N ote : C O 2 is dissolved into water throu gh th e p ro ce ss of d isso lu tio n.) 1. Given that the meta l C alci um Oxide (C aO ) is abundant in E arth ’s cr ust , a nd r e act s wit h CO 2 according to the fo llo w in g ch emi ca l re act io n CaO(s) + CO 2 (g) → CaC O 3 (s), provide a process-flo w re pre se nta tio n fo r th is me chanism th at re m ove s C O 2 fr o m E arth ’s early atmosphere. (N ote : C aC O 3 fo rms as a pre cip ita te - i. e ., a so lid th at fo rm s fr o m a solution.) [3 marks] 2. Suppose the product o f th e mi nera l ca rbonatio n (ca rbonatio n is th e p ro ce ss of d isso lvi ng carbon dioxide in liq uid ) re act io n d eta ile d in Q uest io n 1 a bove :

a. Precipitates at a ra te o f 2 cm/ yr. H ow lo ng w ill it ta ke fo r a 0 .5 m la ye r to accumulate? [3 ma rks] b. Produces sedime nt th at is co mp act ed to a 4 .5 :1 ra tio d urin g lit h if ica tio n p ro ce ss - e.g., due to b uria l p re ssu re. D ete rmi ne th e re su lt in g th ickn ess of th e o rig in ally 0.5 m layer accumula te d in Q uest io n 2 (a ). [3 ma rks] c. Produces sphere s of C aC O 3 w it h a ra diu s of 2 mm.

i. Determi ne th e co rre spondin g te rmi nal ve lo ci ty (in m /s) o f th ese sp here s in water fro m v T ≈ ( 151 r ) ½ , w here r is th e ra diu s in m . [3 m arks] ii. Assuming a nd o ce an d epth o f 2 km fo r an o ff- sh ore o pera tio n, ca lcu la te © L. I. Lumb - Sharing proh ibited. V iolat ors subject to legal and/or academ ic consequences. 1 the se ttlin g time - i. e ., th e time it ta ke s each o f th e sp here s to d esce nd through th e o ce an a nd se ttle o ut a s se dim ent. [2 m arks] 3. After the process of lit h if ica tio n co mp le te s, w hat is th e re su lt in g cl ass and typ e o f sedimentary rock? Obta in a p hoto gra ph o f a re pre se nta tive sa mple o f th is ro ck. ( N ote :

Please attempt to pro vide a n o rig in al p hoto . If yo u a re u nable to d o so , p le ase in dica te your source. Note th at yo u ma y be a udit e d to p ro ve o rig in alit y. ) [4 m arks + 2 b onus marks for an original p hoto .] 4. Enhance your Quest io n 1 p ro ce ss-f lo w d ia gra m to a cco unt fo r Q uest io n 3 . [3 m arks] Over the past 400,000 yea rs, b ut e xcl udin g th e p ast 2 00 ye ars, p ale ocl im ato lo gica l e vi dence suggests that the concen tra tio n o f C O 2 , i. e ., [C O 2 ], h as bare ly exce eded 3 00 p pm .

5. Calculate the percenta ge re duct io n in th e [C O 2 ] fro m volca nic- outg assi ng le ve ls to th is peak value of 300 p pm. (N ote : Vo lca nic-o utg assi ng le ve ls fo r C O 2 a re p ro vi ded in th e “Appendix” below.) [3 ma rks] Inspired by the results of Quest io n 4 , a n in te rd isci plin ary te am underta ke s to g eoengin eer th e sequestration of CO 2 through ve ry-l arg e-sca le mi nera l ca rbonatio n ( V eLaM iC arb ).

(Geoengineering is a dire ct ma nip ula tio n o f th e Ea rth syst em. ) The V eLaM iC arb te am ’s approach includes isolatin g th e re su lt in g p re cipit a te (i .e ., C aC O 3 (s) ), a nd u lt im ate ly buryi ng it in underground vaults imperme able to g ro undw ate r.

6. Obtain [CO 2 ] versus time d ata fo r th e p ast 5 ye ars fro m th e M auna L oa O bse rva to ry.

(Note that you can d ow nlo ad a h ig h-q ualit y ve rsion o f th is gra phica l p lo t in va rio us formats. See “Resource s” belo w fo r acce ss in fo rma tio n.) [2 m arks] 7. Using the graphical p lo t a cq uire d in Q uest io n 6 :

a. Estimate the cu rre nt [C O 2 ] in p pm. [1 ma rk] b. Estimate the a nnual in cre ase in th e [C O 2 ]. In cl ude a n a nnota te d ve rsi on o f th e plot in your solu tio n th at illu st ra te s how th is ra te w as ca lcu la te d. [5 m arks] 8. Based on your answer to Q uest io n 7 (b ), d ete rmi ne h ow lo ng it w ill ta ke th e cu rre nt va lu e of [CO 2 ] to double. (T his will su bse quently be re fe rre d to a s th e “ 2 x[ CO 2 ] cl im ate scenario”.) [3 marks] 9. Suppose the EBCM-dete rmi ned e nerg y, E 2C O2 , a sso ciate d w it h th is doublin g o f th e 1 [CO 2 ] is 1423.9 W/m 2 . Est ima te th e te mp era tu re d if fe re nce , r e su lt in g fr o m th e 2 x[ CO 2 ] climate scenario, usi ng th e St efa n-Bo lt zma n L aw T = (E 2C O 2 /4 σ ) 1/4 - T 0 , w here σ and T 0 1 EBCM is a very simple climate model originally developed for NATS 1780 (Weather and Climate). Additional information is provided via the “Resources” below. © L. I. Lumb - Sharing proh ibited. V iolat ors subject to legal and/or academ ic consequences. 2 are the constants 5 .6 7x1 0 -8 W /m 2 ⋅ K 4 a nd 2 75.8 K, re sp ect ive ly. [3 m arks] i. 10. Rahmstorf (see “Reso urce s” belo w ) est ima te d th at te mp era tu re d if fe re nce s acco unt fo r sea-level changes acco rdin g to th e p ro port io nalit y co nst ant 3 .4 m m/yr p er ° C . U sing th e temperature difference o bta in ed in Q uest io n 9 , e st ima te th e ch ange in se a le ve l fo r th e time span obtained a s th e a nsw er to Q uest io n 8 - i. e ., fo r th e 2 x[ CO 2 ] cl im ate sce nario .

[3 marks] 11. Estimate the wavele ngth o f ma ximu m in te nsi ty co rre spondin g to E arth r a dia tin g a s a black body in the 2x[ CO 2 ] cl ima te sce nario u si ng W ie n’s Disp la ce ment L aw , λ max = w/T , where w = 2897 x 1 0 -6 m· K. [3 ma rks] 12. In which part of the EM spect ru m (belo w ) is Ea rth ra dia tin g u nder th e 2 x[ CO 2 ] cl im ate scenario? What is th e fa te o f th is ra dia tio n? [3 ma rks] 13. Suppose the current e st ima te fo r th e [C O 2 ], i. e ., th e a nsw er to Q uest io n 7 (a ), corresponds to stora ge o f 7 75 G tC in Ea rth’s atmo sphere . ( 1 G tC is a G ig aT on o f C .) If the intention of the g eoengin eere d se quest ra tio n o f C O 2 is to comple te ly offse t th e e ffe ct of the 2x[CO 2 ] climate sce nario , w hat sh ould b e Ve LaMi Carb ’s ta rg et fo r C r e m ova l o ve r the time frame dictate d b y yo ur answ er fo r Q uest io n 8 a bove ? E xp la in . [3 m arks] 14. It is stated that: “The Ve LaMi Carb te am’ s appro ach in cl udes iso la tin g th e r e su lt in g precipitate (i.e., CaC O 3 (s)), a nd u lt ima te ly buryi ng it in u nderg ro und va ult s im perm eable to groundwater.” Why is gro undw ate r iso la tio n a n imp ort ant d esi gn co nsi dera tio n? ( H in t:

The rock type identif ie d in Q uest io n 3 is hig hly su sce ptib le to a ci d r a in .) [2 m arks] 15. Enhance your Quest io n 4 p ro ce ss-f lo w d ia gra m to a cco unt fo r th e V eLaM iC arb approach. [3 marks] 16. Does this VeLaMiCarb in it ia tive fa vo ur th e imp ort ance o f a syst em s-base d a ppro ach ?

Explain. [2 marks] 17. Why might geoengin eerin g, a lo ng th e lin es of th e Ve LaM iC arb in it ia tive , b eco me a necessity? Explain. [5 ma rks] Resources Lumb, I., NATS 1780 lectu re o n “C lima te a nd C lima te C hange”, Slid es | Captu re ( st art - 1:08:54), 24 November 2 016. (I ncl udes backg round, o ptio nal co nte nt o n E B C M .) Lumb, I., NATS 1780 lectu re o n th e “O rig in a nd Evo lu tio n o f Ea rth’s Atm osp here ”, Slid es | Capture (1:08:54 - end), 24 N ove mb er 2016. (I ncl udes backg round, o ptio nal co nte nt.) © L. I. Lumb - Sharing proh ibited. V iolat ors subject to legal and/or academ ic consequences. 3 NOAA Earth System Rese arch L abora to ry, T re nds in At mo spheric Carb on D io xi de. A va ila ble online at https://www.esrl.n oaa.g ov/ gmd /ccg g/tre nds/ . Rahmstorf, S., A Semi-Emp iri ca l Ap pro ach to Pro je ct in g F utu re S ea-L eve l R ise , S ci ence , 315 , 368-370, 2007. Available o nlin e a t http ://sci ence .sci ence ma g.o rg /co nte nt/3 15/5 810/3 68 . (Includes background, opt io nal co nte nt.) Appendix Volcano Halemaumau (Ha waii) [% b y vo lu me ] H 2 O ~ 68%, CO 2 ~ 13% N 2 ~ 8% , S O 2 , H 2 S, e tc. ~1 1% A portion of the electroma gnetic (EM) spect ru m.