The Atmosphere. Atmospheric composition Measures of concentration Atmospheric pressure Barometric law

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The Atmosphere Atmospheric compositio Mesures of cocetrtio Atmospheric pressure Brometric lw Literture coected with tody s lecture: Jcob, chpter 1-2 Exercises: 1:1 1:6; 2:1 2:4

1 The Atmosphere Atmospheric compositio Mesures of cocetrtio Atmospheric pressure Brometric lw Literture coected with tody s lecture: Jcob, chpter 1-2 Exercises: 1:1 1:6; 2:1 2:4 The Atmosphere The tmosphere Thi ski of ir surroudig the plet Descriptio Role of turl tmosphere Effects of chged compositio Atmospheric chge limte UV protectio Acidifictio Helth 1

2 ompositio of the Atmosphere Dry tmosphere (excl. H 2 O): Gs Mixig rtio (mole/mole) Nitroge (N 2 ) 0.78 Oxyge (O 2 ) 0.21 Argo (Ar) rbo dioxide (O 2 ) 365x10-6 Neo (Ne) 18x10-6 Ozoe (O 3 ) x10-6 Helium (He) 5.2x10-6 Methe (H 4 ) 1.7x10-6 Krypto (Kr) 1.1x10-6 Dry tmosphere: Domited by itroge d oxyge Noble gses, i prticulr rgo oc. (O 2 + N 2 + Ar) 1 mole/mole Remiig compoets trce gses: E.g. rbo dioxide, ozoe, methe Humid tmosphere: Wter vpour: Vries, up to pprox moles/mole Hydroge (H 2 ) 500x10-9 Nitrous oxide (N 2 O) 320x10-9 lcultio Exmple: lculte the desity of dry ir t T = 280 K d P = 1000 hp! The tmosphere idel gs (i most cses): PV = RT Desity: = m/v = M/V From the gs lw: /V = P/RT => =MP/RT Air is mixture of gses verge molr mss: M = 29,0 kg/kmole Gs costt: R = 8314,3 J/(kmole K) Isert umbers: = M P/RT = 29,0*1000*100/(280*8314,3) = 1,25 kg/m 3 2

3 Atmospheric ocetrtio of Species Expressios tmospheric cocetrtio: Number cocetrtio: umber of moles or molecules of type X per volume uit of ir Mss cocetrtio: mss of X per volume uit of ir Air compressible These mesures of cocetrtio chge with locl tmospheric pressure Mixig rtio: (No. moles of X)/(No. moles ir molecules) Or: mss X/mss ir Uffected by expsio/compressio Trce gses smll umbers ppm (prts per millio): 10-6 ppb (prts per billio): 10-9 ppt (prts per trillio): Kids of mixig rtios: ppbv (v = volume) bsed o umber pptm bsed o mss Exmple helium: [He] = mole He / mole ir = 5.2 ppmv Mixig rtio = moles of X / totl No. moles = x / Apply the gs lw: = PV/RT = (P x V x /RT x )/(PV/RT) T x = T; V x = V = P x /P = (prtil P of X) / (totl P) Exmple: The mixig rtio of He is 5.2 ppmv. lculte the He prtil pressure t se level! Averge se level tmospheric pressure P = 1013 hp He = He / = P He /P P He = He P = = 5.2x hp = 0.53 P 3

4 Exercise 2-1 i Jcob: The tmospheric O 2 cocetrtio hs durig the idustril er icresed from 280 to 400 ppmv. How lrge is this icrese expressed s mss of tmospheric crbo? m ; d re No. moles O2 d ir molecules 2 1 M Icrese of the crbo mss: M = molr mss of crbo; m = mss of the tmosphere; With kow m : m = 250 billio toes = 250x10 12 kg M m M = ppmv = 120 ppmv = 120 x10-6 M M = verge molr mss of ir m = icrese of the crbo mss Problem How c we clculte the mss of the tmosphere? Hit:The pressure t level is cused by the weight of the overlyig tmosphere 4

5 Exercise 2-1 otiued: How c the mss of the tmosphere be clculted? Grvittiol field d o other forces ffectig the pressure: The pressure t give level is cused by the weight of the overlyig ir Force: m g = AerthP where Aerth = 4R 2 Averge pressure t surfce (P): 984 hp Rdius of the erth (R): 6400 km Reorgize: m = 4R 2 P/g = 5.2x10 18 kg Atmospheric Pressure Depedece o Altitude Verticl elemet dz: Equilibrium: The grvimetric force is blced by the force from pressure grdiet Grvimetric force = Grdiet force dp = - g dz From the idel gs lw: = PM/(RT) dp = - PM /(RTg) dz Rerrge: dp/p = - M /(RTg) dz Approximtio: T idepedet of z Brometric lw: -gadz = (P(z +dz)-p(z))a = dpa P ( z ) P (0) e M gz RT (A = horizotl surfce re) 5

6 Verticl Profiles i the Atmosphere The pressure decreses expoetilly with ltitude Exmple: t 50 km 0.1% of the pressure t the surfce Lud - Helsigborg Temperture profile: Troposphere T decreses with z Erth s surfce wrm due to bsorptio of solr rditio oolig with ltitude due to dibtic expsio Strtosphere T icreses with z Ozoe bsorbs solr rditio d hets the strtosphere Mesosphere T decreses with z Exercise 2:3 lculte the ltitude tht divides the mss of the tmosphere i two equl hlves (Assume T costt t 260 K)! m g = 4R 2 P m ~ P m /2 ppers t P/2 Use the brometric lw: P(Z) = P(0)e -M gz/rt d fid P(Z) = P(0)/2 P(Z)/P(0) = e -M gz/rt = 0.5 Logrithm t both sides: -M gz/rt = l(0.5) Reorgize: z = - RT l(0.5)/m g = 5.27 km 6

7 Se-Breeze Iitilly: T L =T S ; P L =P S ; o wid Solr hetig of ld strogest: Wter hs higher het cpcitivity Evportio of H 2 O cools P(z) = P(0)exp(-Mgz/RT) Differece i verticl pressure grdiet PL PSicreses with ltitude High ltitude wid from ld to se Air colum over ld decreses P L < P S Low ltitude wid from se to ld ircultio cell: 10km horizotlly, 1km verticlly 7

Review Topics on Stoichiometry

Review Topics on Stoichiometry Itroductory Chemistry Review Topics o Stoichiometry Ucertity i Mesuremets Ucertity i Derived Qutity 5.55 ± 0.05 +.55 ± 0.05 8.1 ± 0.1 derived result mesuremets 0. + 0.1 10.0 + 0.1 X 0. + 0.5% X = + = 10.0