Problem_set_02_key - Huxford-Spring 2008 Chem 365...

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Unformatted text preview: Huxford-Spring 2008 Chem 365 Biochemistry, Cell & Molecular Biology Practice problem set 2 1) From Voet, Voet & Pratt (VVP), Chapter 2 Problems 1, 7—9, 12—14 (page 39). 2) The pH of a 0.06 M solution of HNO3 is . pH:—_‘1[R+J : 'J'j(°'°""‘) :, 1,21 3) (3 points) A student in a laboratory at SDSU is asked to prepare a MES buffer at 0.1 M and pH 6.5. She finds a bottle of solid crystalline MES free acid on the shelf and weighs out 0.1 moles. This she dissolves in 1 liter of pure water. What volume of 5 M NaOH should the student add to the solution so that the final pH is 6.5? (MES 1s 2- (N- M0rpholino)ethanesulfonic acid, MW=195 2, pK=6. 15) yK-rh+bjf53__.:::‘:} 3.14 /(1-1'l+l) s 0.6? .. {radian [”5 145;] (.s—ur: (seq, (O-HM‘MM”: 6.061n-eu 014' IO 04 ”I 2 a. “state Add] —‘——‘f 0 061114011st = wmfl = 4) Which of the following weak ilcids would make the best buffer at pH 5.0? ”(M L I @ acetic acid (K: 1 .74x 10 5) P54." '=.‘I ?6 B) bicarbonate (K: 6.3 x1011)?!“ 310.1 C) tris(hydroxymethyl)aminomethane (K1: 8. 32 x 10 9) fk“ g of D) lactic acid (K: 1. 38 x 10 4) Pk‘ =3 9‘ 5) If the pKa of acetic acid 18 4.76 and the pH of an acetic acid solution is 3.5, then the ratio of acetic acidzacetate ion 1s__— h— R pH :91“ +9.3 [llama] A: l1¢efic uul he "-{18 7. Malawi] [Mum] : I 6) The pH of a 0.08 M solution of potassium hydroxide (KOH) 1s . kw - [ea—111+] ~ erw m: .13.... ”M‘ 1,2:- : i am- ,, M 7) What 1s the pH of a 0.25 M acetic acid solution (pK: £7%)1flv when 2/3 of the f H“ v ll", acetic a01d1s 1n 1ts lonlzed fcnr__r_r_1_? —'>(}.¢,g~h+¢ 5.“, “(’59. ') m\_ a: 312 P rM-M .,, 4 am $12- 8) Approximately what volume of 5 M hydrochloric acid should be added to one liter of 0.1 M Tris (pKa = 8.1) buffer to change it from pH 8.5 to 7.5? F“: ?h* 1.7 mls hflj [mg 4441] loss-3.1 : [ms ha] _ 2.5' 25/(1,gH)—_Df.}/ [MEN-ll} 0.?! NM : Mam»! ow 91 [1mm] 3.35; b rat/(o tguj- o w [mud] l mm)“: (Lu-0.1“: 0.010»! W Lemuel/5M:- '7 [ms nu] 1° ...
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