Analytical exam 1

Analytical exam 1 - f // a __ __ Midterm Exam l. t. »...

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Unformatted text preview: f // a __ __ Midterm Exam l. t. » ANALYTICAL CHEMISTRY 227 March 4, 2009 /\ Directions: Answer questions on these sheets. SHOW ALL WORK. Do all work in pen. Use proper number of significant figures and give units of answers requiring them. Some equations that might be useful: s : [Z(x — x)2 / n-1]1/2 pH = -log[H3O+] [OH'] = [(Kw/Ka) x [salt] ]“2 Kw = 1 x 10“4 = [H30+][OH’] 1. a) Name the indicator you would use if {you were titrating a solution of KCl with a standardized \ solution of AgNQg ' ' j 5 ug’ r5 (5 r n e— 29;” (I I} ,e ,/ “‘- b) Name the indigator you w uld use you were titrating Na2C03 with a standardized solution I p 0f HNOL/‘w’ ’6 } f§=7:'lz,":;3'l- W"? V (95 0 0‘ L“ p '0 "1 I’Y‘ .r 2f 80'” ,7 r~ 6’1' "" (1/4" F b) Name the indicator you would use if you,were titrating a solution of KOH with a standardized solution of HClO4 3’ W“ :0 #3" a"). a, A"? “m 2. Calculate the pH of the following aqueous solutions: a) 0.0133 M HClO4 , 1.59/7: //02<0'03//33) _ WW-..“— b) 0.345 M Sr(0H)2 pay: "IOGCJJQ"? I ~ 0.3,“, 02%,; ,V MMaowl c) 143 of 0.1023 M HN03 to which has been added 38.10 mL of HNOg solution whose M .1 pH=2.l3l. m mmo'(§0(/43N03 :[/H'O)>v{0'/02-9N‘ f /' §qum. / [,2.l? A :3 [0304)? ,M ./~3~’~‘1{y}g «f ' nap/r; of HJ/fiwfl; 894%“ 7W! .. . moi/3 0F n30." :, 3/8 m m I pH; ,«Ig’fl; .é' ‘vmfll..im4;i2 9..“ M) /‘:/; 0 '0 3 9m» if; mm ! r" (X 2 N1?” / r HEX“ .. ‘ y /. (7% 3. Given the following results for replicate measurements of a copper solution by anodic stripping voltammetry (ASV): 22:71, 2L9, 2-23, 2A2, 2%.}, 224 ppb (parts—per—billion): 2 a) Calculate the mean (show work; answers alone will result in no credit): WW w 2+ *2?— <1 _, -7“..on «a.» um... MWWWW, ' " “2:” [\b) Calculate the relative range (in ppt) (Show work)?“ \>\ 1 I f U 0 0/ /’/I Feta“) Via “ fie/Mw/QWW / war/“(7' War“ ##wiq “ //~’/ (c) j) Use the Q—test to decide whether any of the values given above can be rejected at the 90th _// percentile. [Ifyou can reject one or more data, specifl which one(s) you will be rejecting, and show why (Show the calculations)]. If you find that you should not reject any data, say “reject none”. Rejection quotient (Q-test) Table N Qt 90th percentile) ;‘ 4 0.76 ,7 _ 0.64 7 0.51 /r d) If you decide to rejectkany datain c) above, recalculate the mean leaving this (these) data out. WM“ 5 X1 22" + 2’ "’7 t 2 21' '3 7"” ‘75) .«w—anJmH» ..«»~..y.u...ng,.. . _ 6) Now, calculate the relative range (in ppt) once again. / 2 2’2. 4. a) Calculate the pH when exactly 1.00 mole of sodium hydroxide solution has been added to ‘ 3 1.00 mole of the diprotic acid, linoleic acid. (K31 _=_,l .34 X 10'2; Kaz = 1.69 X 10's). M 2 /00 r MZ/l +‘N0vzmw3 Hfl’ c) What is the pH of the 301566;}: when 2.10 moles of NaOH have been, ad ed to 1.00 mole of linoleic acid? Assume the total volume at this point is 102.1 mL. MOMS 0/" Newer/7:2 2-/0 ma k) af 136,. “,4, :fl/ 0Q”. f \ swab) 5. Calculate the answer to the following‘numerical problem: '_ (753.342 + 2;33)x(0._99.85) / (202.4356 x 2463);“) L4, g g ‘c, I i) 7 ">1 l y W r \ It? 6. Why is it necessary to boil the soda ash unknown solution near the end of the titration with HCI? (Be VERY specific; it is not sufficient to say “to expel the excess steam”, or whatever. I want you “to tell me EXACTLY why you have to boil the solution = use an equation to justify your answer). ./__ (L75: Maw} er HC/ tit-7* U *1. ’ c’ 5 $6047 9‘2) 54m 3 ‘33 1w 9: an?“ L w m. :59 /'/7, (r C 3 “i” Viv/67 6 / SO’MA’W M‘W m (and 0/17!“ch 431;!» TAJRA luv! 7’7“ "M‘KI’V @(4' Y’M C7{ Céflmwoy‘iw 1? f . 4 _ (AW “416/ /7 65 [ha/Lby a/L/Z/LZJV‘ ,LK, // [a]; U/ [M C/lx M" / ’ / f M c M M 1” WM m a4 0/ r/‘7/ 14"" “A i gum camif AL) [8» ..—-__fi \ EXTRA CREDIT: . r r _. ,M 4, 122.32(+/— 0.05) — 2.2143(+/- 0.0010) + 14.261(+/— 0.007)= J ’ g ’X) Q, (L ‘3‘" n‘ f I" flbSNML Err“ ’ $1 "671—65 z "‘ (0053 {hi/000110)? 0 0Q «r v V b) Find the relative error for the above problem. I I V; 4- Qf/mh’ {my 9 (fi/ESUV\ . \ ‘ {ZIO' ...
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This note was uploaded on 05/19/2010 for the course CHEM 227 taught by Professor He during the Spring '10 term at Rutgers.

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Analytical exam 1 - f // a __ __ Midterm Exam l. t. »...

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