Question

Problem Set 15 CHEM 1252 November 10, 2019 Textbook Reading Assignment: 15.5-8 [and see App. 5 for Kor k, values] Additional Practice Problems: 15.51,57,59,61,63,65-66,69-71,77-78,80,84 1. Calculate the concentration of an aqueous HNO solution that has a pH of 2.45. 2. The på, of hypochlorous acid (HOCI) is 7.53. (a) Calculate the K. of HOCI. Given that the pk, of hypobromous acid (HOBr) is 8.63, which acid is stronger, and how do you know? (b) Write the reaction (with physical states) that corresponds to the K, of HOCI. Identify the weak acid among the reactants (label it WA) and its conjugate base among the products (label it CB). (c) Calculate [H3O+] (or "[H]") and pH for a 0.15 M HOCI solution. Check that any approximations you make are valid (cause no more than 5% error). (d) What percent of the total HOCI has dissociated in a 0.15 M HOCI solution? Would the percent dissociation increase or decrease upon dilution, and why? 3. Explain why the pH of a 0.050 M H2SO4 solution is not 1.00. Will the actual pH be greater than or less than 1.00, and why?

Answer 1

U augwer PH = -log (ist] 2.45 = log (M+] - . [ht] = 10-2.95 = 3.55 x 10-3 m . [MNog] = [mt] = 3.55*10-3 m are in l. i molar raheo) pka of Hocl = 7.53 -lag (ka) = 7.53 causwa) lag hem Ka of Mecl = 10-7.53. = 2:95x10-8 pka of HOBO = 8.63 Ap pka of MoBo > pka of Moci; so Hocl és a Stronges acid as higher the pka lower the Ka (le. acid ionization conglent meaus les dissociation). 6 HOC) (aq) + Mzol) = WA Hoch(aa) + H2ol1) I: 0.15m Mgot (aa) + ocr(a) C Hot(aa)t ccrlag) tx +x E: xm (0:15 -3C)m xm Ka= [Mgot] [oor] [MOCIJ - 2.95 x108 = x2 (0.15-x) Now (0.15-0C) 2015 ap ka is very low : x2 = 2.95x108x0.15 0. 4425 710-8 x= 6.65X 10-S . [Mgot] = x 2 6.65X105 m ( answa)

A. @ Pereant dissociation = thot x 100%. CHOCI = 6.6sxlors mx1004. 0.15m = 0.0947 Percent dispciaton will increase with dilation hydraten energy now increases. as