Chem 222 Quiz 6 Apr 26, Chem 222 Quiz 6

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Beverly Hunt
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1 Chem 222 Quiz 6 1. Do not open this page until you are asked to start. 2. When you submit the answer, return only page After your time is up, please bring the answers to the instructor within 1 min. Any answers collected after 1 min will be subject to 20 % reduction or will not be graded points each. You can earn up to 20 points if your score is over 20 points. 1

2 Name: Circle Your Section: M/W 8AM M/W 11AM M/W 2PM T/R 8AM T/R 2PM 1-2 Manshui 3-5 Yangsoo 6-7 Tapa 8-10 Ginny Sujeewa 1. Cycle the answer with the correct number of significant figures. a) = 12 b) ( ) = c) ( ) + ( ) = d) log ( ) = Which of the following expressions is not correct? a) 1.00 mm = M b) 1.2 cm = m c) nmol = µmol d) 1.28 kg = mg 3. KHP is a salt of the intermediate form of phthalic acid. What is approximate PH of 0.15M of KHP? (pk 1 = 2.950, pk 2 = 5.408) a) PH = 2.2 b) PH = 4.2 (pk1+pk2)/2 c) PH = 6.2 d) PH = 8.2 e) PH = The amino acid, Arginine, has the following forms. H 3 Arg H 2 Arg HArg Arg - Pk 1 =1.82 Pk 2 = 8.99 Pk 3 = What are the principal form and the second most abundant form of arginine at PH=10.0? Principal the second most abundant form a) H 2 Arg + H 3 Arg 2+ b) H 2 Arg + HArg c) H 2 Arg + Arg - d) HArg Arg - e) HArg H 2 Arg + 2

3 5. There are two different acids in each beaker. One beaker contains weak acid ( M, 100 ml, pka = 6.00). The other contains strong acid ( M, 100 ml). These acids are titrated with strong base, 0.020M NaOH. Choose the answer that gives closest PHs for weak acid and strong acid at the equivalence point? PH of weak acid PH of strong acid a) b) c) d) e) When you are titrating 0.1 M KI, KCl and KBr solutions with 0.05 M AgNO 3, you obtained the following titration curves. Then, the order of K sp of AgI, AgCl and AgBr should be a. K sp (AgI)> K sp (AgCl)> K sp (AgBr) b. K sp (AgCl) > K sp (AgBr) > Ksp(AgI) c. K sp (AgBr) > Ksp(AgI) > K sp (AgCl) d. AgI, AgCl and AgBr all have same K sp e. None of the above 3

4 7. When you titrate excess EDTA added to analyte with second standard metal ion solution that time you call the titration procedure a. Direct titration b. Indirect titration c. Back titration d. Displacement titration 8. From the following reduction potentials: I 2 (s) + 2e - 2 I - I 2 (aq) + 2 e - 2 I - Eº = V Eº = V I e - 3 I - Eº = V Choose all the correct statement(s). No points unless you answer all correctly. (Hint: E 0 = ( /n)LogK ). (a) The equilibrium constant of reaction: I 2 (aq) + I - I 3 - is 300. (False: should be 747) (b) According to the equilibrium constant of I 2 (aq) + I - I 3 -, 0.1 g of molecular iodine in solid forms can be dissolved in 100 ml water completely. (c) The reaction: I 2 (aq) + I - I 3 - is spontaneous at standard condition. (d) The reaction: I 2 (s) + I - I 3 - is spontaneous at standard condition. (e) The equilibrium constant of reaction I 2 (s) + I - I 3 - is We got laser with wavelength of 663 nm in the lab. As following, which statement(s) is correct? Choose all. No points unless you answer all correctly. Planck s constant h = Js and a velocity of light, c = m/s. (a) Every photon produced by laser (λ = 663 nm) carries 3.00 x J/photon. (b) The frequency of a photon is 1.87 x Hz. (c) Excitation is based on the intensity of light source, so we could use laser with 663 nm to excite the UV range absorbance of molecules. (d) The wave number of the photon is 1.00 x 10 4 cm The following is the unbalanced reaction: Cr 2 O Fe 2+ Cr 3+ + Fe 3+ Which statement(s) is correct for the reaction? No points unless you answer all correctly. (a) The balanced reaction is: 1Cr 2 O Fe H + 2Cr Fe H 2 O (b) The balanced reaction is: 1Cr 2 O Fe H + 2Cr Fe H 2 O (c) Cr 2 O 7 2- acts as a strong oxidant in this reaction. (d) Overall reaction, Cr 2 O 7 2- was oxidized by Fe 2+ (e) Fe 2+ was reduced by Cr 2 O

5 11-13 To answer questions through 11 to 13 use the following schematic diagram and the provided information regarding the electrochemical cell. Switch P Light bulb Switch R - + Cd electrode Salt bridge Ag electrode Cd(NO 3 ) 2 (aq) Ag(NO 3 ) (aq) : Battery 1.5 V Cd e - Cd (s) E o = V Ag + + e - Ag (s) E o = V 11. Consider the following statements about the above setup with 1M of electrolyte (AgNO 3 and Cd(NO 3 ) 2 ) A. When switch P is closed or turned on (switch R is open or turned off) the setup works as a galvanic cell and the light turns on. B. When switch R is closed or turned on (switch P is open or turned off) the silver ion is reduced. C. When the switch P is closed or turned on (switch R is open) Cd electrode functions as an anode. From the above statements the incorrect statements are a) A, B and C b) A and C c) A and B d) B and C e) Other than a)-d) 5

6 12. Assume that the light bulb in the above circuit is replaced by an analog voltmeter and switch P is closed or turned on (switch R is off). Both the electrolyte solutions are M. The reading in the voltmeter could be a) V b) V c) V d) V 13. The potential of a galvanic cell could be affected by A. Temperature of the electrolytes in half cells B. Concentration of the electrolytes (ions) in half cells C. Kind of a reference electrode when a reference electrode is used as an anode a) A, B and C b) A and B c) only B d) B and C 6

Chem 222 #29 Review Apr 28, 2005

Chem 222 #29 Review Apr 28, 2005 Announcement Please meet me after the class if you have any conflicts with the final exam schedule. You can expect similar questions with Quiz 6 in the final exam. If you