# CW 18 - CHM 2046 Class Worksheet 18 1. Predicting...

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Unformatted text preview: CHM 2046 Class Worksheet 18 1. Predicting Spontaneity Using AH and AS. - A reaction tends to be spontaneous if AH = "" and/or AS = ' 4" . IF THENPredict _ AH=— and AS=+ I; Miami/am (3 L; M: R) AH=+jand AS=— W11" W04?“ch (*7an £3 ‘ As=+. § grewjawxbl? «AM ‘hncj‘F-ti’L-sbv AH:——— and AS=-—, ‘”. 7‘1”? W '7" 2. Predicting Spontaneity Using AG = AH - T AS. ‘Ma 5 Fry. (5 n 43% “:- -~ , 'ruﬂitgnlﬁ 1 £1 D (3 3 ‘r I u . v" 0-? t L I . - Calculating AG°: I Using Tables, like with AI-I° (AG° for elements = 0) - Using AG° = AH° - T AS° hem: For reaction as H200) Ii H20(g), calculate AH°, AS" and AG° at 25 °C. a __ "" lei}va ‘fr by“): (,ZLHJQJ“( 2-9/5 g) [31.10: gtég"0iC‘/rmo\ “DSHQOgggeﬂ EQI'QJT/IMWASE H‘M ‘j/molfd 930 t “22W "#237! LT/MO(AG°=_9i_‘EI)mJ ( n 7 Oh,- ba; Qqq— ‘242ng,1<(n9-a,i ' .Fhal' :2 g" max 10 “j o Effggtgﬁjljgn A§i°=AH°-TAS°andspontanei : tr»- .ovo’l'; bGaw AND g—o bH MWV‘" haww 3+ , (ﬂ - ‘ ' "’w a p - AS Mimzm 30"”“n-t M Legw’ﬂﬁg - ——‘Y‘/>S ' For H2 (1) #H20(g),AH°=+and AS°=+ u AtlowT Ag”: +— 3.0 \$75.“ w batik"113M,.—:lt'.:‘~v.._n.—.=>m u AthighT 45:30qu s» «w 9 ' F0r2N02(g)s-‘N204(g),AH°=;and AS°=; u AtlowT 5‘30"?” 3—9 Yuan-A13 n A YEA—awn n AthighT 4503": -+ to «(will {4, “0+ mosaswwm, - Co(OH2)6+2 (aq) + 4 c1- (aq) ? 00014-2 (aq) + 6 H20 (1) ‘. Qbsmedmtmﬂtlﬁsshiﬁs EA” antlathighlthisshifts 3‘ 53m mums: signs of AH° = and Ase =+ ﬂ...— m: For H200) # H20(g), assume AH" and AS° are constant with changing T. Calculate the equilibrium temper-nature (the where of AGO = 0 = AHO _ T Asa). 1‘} D to: “ll/Own lTbS :43:- H- . I I .2— ‘5 -" :1 5 AH‘” ,, ht, —0 km - use; ,Z‘fmzu \<;. aft st; "l7: Eda. bu 4: \$31111 _ sh”. "I “444‘” w“— : 310 k. T=§20i§ waft». loo: la a} 3. Relationship of AG" to the EquilibriumK. 37 g R AG°=-RT ln(K) useR=8.3l4 J/mol K) inﬁerbra K: egg) : ME? 7 ,l W R 1 . mum: Calculate K at 25 °C, for H200) v! H20(g), using the AG° ﬁ'om above. Also, convert the vapor pressure of water at 25 °C (23.8 'mmHg) into atm and compare. K _, Q 9 8:5” kj/AWD (legible) _ 6.3L} .44, (875”! ) (Lalgﬂli) —» La ¢ . ll: ‘ . K(at25°C)= 00301 :— PH20(at25°C)= 0.038an . 4. Solubility and Complex Ions. (Text section 18.6 is recommended reading.) We have discussed how some sparingly soluble salts are soluble in acids, such as how CaCO3 dissolves in HCl(aq), but this won’t work for AgCl since Cl' is not basic. The other “trick” to dissolve “insoluble” salts is to form a complex ion. AgCl dissolves in NH3 by what can be considered-a 2 step process: AgCl (s) 6* ,.AsF‘(éiil/+ 01- (ao. Ksp = 1.8 x 10-10 /”g”'('aq) + 2NH3 (as) g Ag(NH3)2+(aq), gimme? 4 -_—__w _'_"'_‘—'“ up; , l , .. F I v ' 0,4!) It aka) + 210wa .5. N44322:: Ute)?!” K .0 9’21 )(l 6249 W K : O r 0 0.233; a; Combining the 2 equations and K’s suggests that AgCl is rho} wire/l1 soluble in NH3. Using a high [NH3], however, can shift the equilibrium to the right. Eminent: (a) To dissolve 0.10 mole AgCl in 1.0 L of a NH3 solution, what ﬁnal “at equilibrium” [NH3] is required? Hint: what will be [Ag(NH3) 2+] and [Cl']- in the ﬁnal ' ’ :l' - (with. , , ,m d/Lq“ w"- W C“? , le/gdLL 4/15 otaglqcrlﬂg3>lﬁj :1 O'lgn‘o‘ :_ o,ng,[U LHAL WLbﬁLA,JA[d .2. (IL— >(OI3 Kl ﬁaCNHszf] (8” L ' it w 3%,,2sg'xxpﬁl : 6 ti“ ...
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## This note was uploaded on 03/27/2012 for the course CHM 2046 taught by Professor Veige/martin during the Spring '07 term at University of Florida.

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CW 18 - CHM 2046 Class Worksheet 18 1. Predicting...

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