Name: March 28, 2007Lehman, Spring 2007

Part I istry 142 ~eparationI

Directions. You will work out the problems on thi4age then enter them on the computer. Once you enter them into thecomputer you can submit your work\for grading. ~~can re-enter (and re-score) the problems as many times as you wish.

Qu~on 1. KOk ~Cid'~r~~;Who'i, ilieP; of~~~;;tiooo:;a.0-.. j[H-A.:J = tl> -=0 (c;.1L-I9-i)

~ ::- 3. Co 4 )(lD- S

f J.+-'".?,. y ~

Question2. An identical amount of an indicator solution was added to a series of 5 buffer solutions of pH 8,9, 10, 11,and 12. The color was blue in 8, purple in 10, and red in 11 and 12. The pH 8 buffer sample registered 1.09on the absorbance scale and the pH 10 gave a reading of 0.290 at the same wavelength setting on theSpectronic 20 spectrophotometer. Assume that only one species (HIn or In-) of the indicator absorbs at theselected wavelength. Calculate Kafor this indicator at pH 10.

Ka-,.-- ~-rJUvlJ

~rfl1-(i rID1.6t~CJ/A~D) ID~

C).~~D

{) .1--L,1-/6/D

--'

K ~ :;:;

Page 1 of 11

An identical amount of an indicator solution was added to a series of 5 buffer solutions of pH 8, 9, la, 11,and 12. The color was blue in 8, purple in 10, and red in 11 and 12. The pH 8 buffer sample registered 1.23on the absorbance scale and the pH 10 gave a reading of 0.295 at the same wavelength setting on theSpectronic 20 spectrophotometer. Assume that only one species (Hln or In-) of the indicator absorbs at theselected wavelength. Calculate % dissociation for this indicator at pH 10.

[~rnJ DL~5

[HTnJo

[W-:CYlJ0\ts.S ::; GcV1~ ==

Q-tr:{)J 0 ::;- !.~3~-l.9-3-().~ 6 'f\ O- L:l3 X lu

Name:

Question 3.

%D~

March 28, 2007Lehman, Spring 2007

x. LuG

L~3- ().~45

An identical amount of an indicator solution was added to a series of 5 buffer solutions of pH 8, 9, 10, 11,and 12. The color was blue in 8, purple in 10, and red in 11 and 12. The pH 8 buffer sample registered 1.07on the absorbance scale and the pH 10 gave a reading of 0.293 at the same wavelength setting on theSpectronic 20 spectrophotometer. Assume that only one species (Hln or In-) of the indicator absorbs at theselected wavelength. Predict the absorbance of this indicator at pH 9.

Question 4.

K~ ~I 6/0

-to~ . ~5 x. tD .:::::

)c,~

(LOt-0//-.93 )C).?-q 3

-' 9. .051..1£/°

I O~ (\.0,+ ---1c)- )G /-

cJn ~ \!-t~~

Page 2 of 11

Name: March 28, 2007Lehman, Spring 2007

Question 5. A weak base, B-, has a pKb of 5.52. A 25.00 mL aliquot of 0.137M B- is titrated with 0.082M HC!.Calculate the pH after 18.05 mL of acid are added.

~ 8- ~ tfGlaJJJ: O.O;:)SOO(O.I61t3~2Sj,li3

~~ Hel ~: ~ . 01~OS (0'()r,~ ~ /,Lf,?:ox:IO-i~ g ~ ~': 3.4Q,)XI{53_1.4iOAI63<,-l.9lfx 16-3~H-B ~ ,fJvWY. l,L{ 'is' X 10:'>

C .l../S)( IIr3 JI 0 5.'~ of).DL/3D5" .- )L ~ -

(l.'\.:l'k..lO-~.- ~ J0, ol..(305

1t- =- [6W-j

Question6. A weak base, B-, has a pKb of 5.52. A 25.00 mL aliquot of O.lOOMB- is titrated wi~hO.lOOMHC!.Calculate the pH after 25.00 mL of acid are added.

1L~~ . ~~B ~ ~ /-i+ + ~- u f>~= g.4~

~ rtB '" Q. enS 60 0. [) ::; () .eo2':;;roB- ~ H'"--? HE. r;fZ- ~ IHB1-$SF tk.-l~~ \~@)l ~

{-\ B :p\ed~c.eJ-. .

f\ -:; [~t!+) CBj - - )G:'>' - A,,<{~

<-. CIW>J. - C:>,6()~ '-"' . \ - t 0t) .f!J5r£o

-y =- l\{4-)

Page 3 of 11

Name: March 28, 2007Lehman, Spring 2007

Question 7. A weak base, B-, has a pKb of 5.52. A 6.63 mL aliquot of O.148MB- is titrated with O.154MHCI. Calculate

-;:':O~cid:W:' :f1)'fi/ ~ ~ fM~ ~~ ~¥!:1~' ,\ -3flAM 0C1 :IN "7 C!z . e I0 lf- )) .[~4) ~ Is"" )LID

~B- <0 e.e()(Pfo3(p.It{~~<1/iSl)(IO-i

fi1~ lie! af/i1~ ~ t. $rX ID~ <f.i/AIlr£!G :;; S-~ ~~Y-l 04-

5.«,5 i-l ~~Lf . =" ?".lfi X t0 ~2:::-U+~I. G/{, X 10 f'14 ~ -/ &d-fH-+-J:O-

Question 8. 25.00 mL of an acetic acid solution are titrated with 36.00 mL of 0.1234 M KOH solution. The Kafor aceticacid is 1.8 x 10-5.What is the molarity of the acetic acid solution?

l+C-~Hj)L + KvH ~ K~~a°,- t- f-tJ)

[kED #\ L 1\0HI( .12; 1~~«:J(l-- ::;-[fre&;fKrL 1 ~ I\~H 8. {Y.5WL

Question9. A solution of the compound, X3Z, is found to have a Z3- concentration of 0.000 10M. Calculate Ksp for thiscompound. Calculate your answer to 3 significant figures.

'1.32-- . ~ 3;<.4- +- -:[~-

K$f <= C1(1 ?'[~J3 . \\ ~ -~

~>( tJ.L>80ltJ) CD.t9eo toJ :; d.. T X 10

Page 4 of 11

March 28, 2007Lehman, Spring 2007

Name:

Question 10. 4.67 g of AgZS04 are placed in 1000 mL of distilled water in a 2 L beaker. After sufficient time is allowed,how many g of solid, undissolved silver sulfate remain in the beaker? Ksp for silver sulfate is 1.2xlO-5.Assume that the addition of the silver sulfate does not change the volume of the solution.

K~r :; CI4fJYW'i'2--) := l.~>UD-S-

('L1G)9-(1?)~ !.?J(slD-S-~ -2-

A ~ ~~ l{4,L?' '" [.'2. )( 1 G -> '1L- -::c I. 4S:AlO~ -2 -244 I.LfS:XIO ~ 1. ~ S-KJD ~E>\ D Il,~~ - ~.S"R~

-\efJD~L X -l~~ ~ leW~L

Lf. &i ~4.s:2-::- O.l~d ~Question 11. Write a balanced net ionic reaction for each of the following dissolution reactions, and use the appropriate

Ksp and Kf values in the appendix of your text to calculate the equilibrium constant for each.

a) Zinc hydroxide in aqueous NaOH to form Zn(OH)l-

~"" ((jI-)2 .- ~ ~t-~- ,/\",;"'" L1.1 '/-.10-1?-

7 ~ ~ I-\-

- ---=:>/ (I-. r) '2.- 8 IS-

~ +rlDl ~ t:::Yll9l-r 4 K+:: +.<6XIO~ 6 )(10

6Y\(P~\ + ;<6H- .;>~,"{DH)~- f\~Kspt\;:5 X IO'~

K'" ~ I"-10-(1)(~ Jb) Copper(II) hydroxide in aqueous ammonia to form CU(NH3)4Z+

Cll. (01+1.::;::::=:= ~T ~e 1-1- (\",p" /.rv)( lD-I'l

~+ !fJJ~ ~ ClAQJH~)4e.i- K-¥-:; S.('oXlOlI

CIA(Mf \. T 1.fJ-Jfl-s - CIA QJH3,~2.++~f)i-l-K =- K~p r\f-

K",- l,~)<..ID-I't (5:(0)(10')Page 5 of 11

Name: March 28, 2007Lehman, Spring 2007

c) Silver bromide in aqueous NH3to form Ag(NH3h+

AJBr ~ ~+ Br-))f+ QNf4 ~ 11 ().;Hal+--

/{} [!;r-f-~IJ~ 4' 13 (iJ~): + 1?r-

Question 12. What is the molar solubility of barium hydroxide in water? Would you characterize barium hydroxide asbeing "soluble"? Why?

'b<L (bt})~ ~ g.!+ {- ~~bt ~

1\sr<' [&.?-rj [pW12

Kf ~ ~ 1::- (1-'F y-- c:--4~~l~¥r ~ {WL~ ~

4~t\,~~~

;:c-~ /.0tt4-~

Question 13. What is the molar solubility of barium hydroxide in a pH 9.0 buffer?

Ksf", (y)Cf(/)'~ L-~5' -1p~ Wt&Wt ~kt,t i~

Page 6 of 11

Name: March 28, 2007Lehman, Spring 2007

Question 14. For the vaporization of benzene, I1Hvap= 30.7 kJ/mol, and I1Svap= 87.0 J/molK. Calculate I1StotaIat 70°C.

iJ S $.IA {'('=- - DoW V(t.. P~ '. J:J <; S 5~ 1\ S ~f'l' J Y 1tJS'

LlSa, ~ .bS?s~rr + AS s'1$j bs's...rr:- -~) {J ~~34:3(\

A r t" . 4 S~tA-rr -= - '6~.S-TfK~~ Sn>\-:; ~1-.017 I ~ +- - <6~..s- J/

.\

/1'\ B \'- ,{..el~ :::- -;) S SfI1'l8(

Question 15. Will benzene boil at 70°C? Why?

}J~) -rk ~~L1 S ~r ~

~;Mf ~~d~

Question16. CM' ~~;gpnn1b~m;;o~0' 0"' ioor.

6Sre-r ~ -~C07-GtJ~~K-'" -t-

X

t: ::: 353 K) tOt) G

\S+.G1~/(~O

Question 17. For melting of NaCl, I1Hfusion =30.2 kJ/mol, and I1Sfusion= 28.1 J/molK. Calculate I1Stotalat 1050 K. Watchyour significant figures.

J\ s ~ ~~J r-.LJ s. (A ( r -:;; . ,t.L..s

T~SI8T~ ~<6.lT/

\If« yvt~

J-30) ?...tJ()~8 t- ::. -- {D50 K

+ d~.<6 0J:~ ~

-:;:: -2&'.'&%"",t

- (). 1- Jj~W>t

Page 7 of 11

Name: March 28, 2007Lehman, Spring 2007

Question 18. Does NaCI melt at ~K? Why?

M}~bC;w-rM-T'

Question 19. Calculate the melting point of NaCI. Report your answer in DC.Report your answer to three signficantfigures.

0~g.\ WK) ~O

Part II

Question 1. Discuss chemical spontaneity in terms of movement towards or away from equilibrium.

Page 8 of 11

tJG TbT-t:.ey e>"

::;;; ..J I'\el 1(

)(-t

X := I01-K