Name: March 28, 2007 Lehman, Spring 2007 Part I istry 142 ~eparation I Directions. You will work out the problems on thi4age then enter them on the computer. Once you enter them into the computer 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~~~;;tioo o:;a. 0-.. j[H-A.:J = tl> -=0 (c;.1L-I9-i) ~ ::- 3. Co 4 )(lD- S f J.+-'".?,. y ~ Question 2. 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 1.09 on the absorbance scale and the pH 10 gave a reading of 0.290 at the same wavelength setting on the Spectronic 20 spectrophotometer. Assume that only one species (HIn or In-) of the indicator absorbs at the selected wavelength. Calculate Kafor this indicator at pH 10. Ka- ,.- - ~-rJUvlJ ~rfl1- (i rID 1.6t~CJ/A~D) ID~ C).~~D {) .1--L, 1-/6/D --' K ~ :;:; Page 1 of 11
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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.
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.
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?
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+