Worksheet 17-Blandishments

Ofa)b) 0.821 M HF and 0.909 M NaFc) .0.100 M HF and 0.217 M NaFd) 0.121 M HF and 0.667 M NaFe) They are all buffer solutions and would all have. Which mixture-should be chosen to prepare abuffer with a pH dose to 3.4? .AcidAcetic acidAmmonium ionHydrogen carbonate ionHypochlorous acidNitrous acid(A) NH4NO3 and NH,'(B) HOGlandNaOClFormulaCH3COOHNH4+HCO3-HOC1HN02(C) CH3COOHandNaCH5COO(D) HN02 and NaN02(E) NaHCO~andNa2C03*a1.7 x icr55.6 x 10-104.7 x 1CT113.5 x Itr84.5 x ICT4The solubility product, Ks, of Cap, is 4 x 1CTU.Which of the following expressions is equal to thesolubility of CaF,?s\ What is the pH of a solution made by mixing 200 Isulliliters of a 0.20-molar solution of NH, with 200m-Uliliters of a 0.20-molar of an NH4C1 solution?(The base dissociation constant, J^, for NH, is 1.8 x(A) Between 3 and 4(B) Between 4 and 5(C) Between 5 and 6P). Between 8 and 9(E) _ Between 9 and 10 ' IWhich one of the following is a buffer solution?A. 0.40 MHCN and 0.10 KCN\0.2GMCH3COOHC. l.OMHNOs and l.OMNaNOsD. 0.10MKCNE. 0.50MHC1 and0.10Hadthe same capacity.Sg) What is the solubility-product constant~ expression for the equilibrium formed bysolid Cr(OH)3 in solution?(C) JT - [Cr3+p[OH-(E]K I=[Cr+][OH-]3/[Cr(OH)]IpWhat is the volume'of 0.05-molar HC1 that isrequired to neutralise 50 ml of a 0.10-molarMg(OH), solution?(C)P)100ml200ml300mi400ml500mlA solution of a weak base is titratedwith a solution of a standard strongacid. The progress of the titration is followedwith a pH meter. Which of thefollowing observations would occur?A. The pH of the solution graduallydecreases throughout theexperiment.B. Initially the pH of the solutiondrops slowly, and then it dropsmuch more rapidly,C. At the equivalence point the pH is 7.D. After the equivalence point, the pHbecomes constant because this is thebuffer region.E. The pOH at the equivalence pointequals the pKb of the base.Which of the following is the least soluble?(A)CaS04(B) BaF2(C)NiC03(D)CaCrO4CE) Sn(OH)2£ =9.1 10-*K. = L.010^Ksp = 6.6 10-14Ksp = l.i 10-4Ksp= 1.410-28

1412 -I10 -I6 -I4 -f10 15 20 25 30 35Volume of 0.1 M NaOH added (mL)A 1.0 L sample of an aqueous solution contains0.10 mol of NaCl and 0.10 mol of CaC!2. Whatis the minimum number of moles of AgNO3 thatmust be added to the solution in order to precipitateall of the CI~ as AgCIO) ? (Assume thatAgCl is insoluble.)(A) 0.10 mol(B) 0.20 mol(C) 0.30 mol(D) 0.40 mol(E) 0.60 molThe plot above shows a titration curve for a 0.1 Msolution of a weak acid titrated with 0.1 M NaOH.Which of the following pH values lies within thebuffering region of the solution?A laboratory technician wishes to create a"buffered solution with a pH of 5. Which ofthe following acids would be the best chokefor the buffer?(A) H&0,.(B) H3As04,(C) H2C2H302/(D) HOC!,-(E)HCN,K = 5.9 X 10-2Ka = 3.0 x 1Q-8X = 4.9 X 1Q-1DWhat is the pH of a mixture of acetic acidand sodium acetate where the ratio ot[CH3COCT1 / [CH3COOH] is 4.00?TheK ofCH,COOHis 1.8 x 10^5.3 3(A) -logCl.8 x 1(T5) - log(4.00/LOO)(B) -log(1.8 x 1Q-5) + logf 1.00/4.00)(C) -logtl.Sx 1Q-5)(D) log(1.8xlO-5) + log(4.00/1.00)(E) -log(1.8 x ICr5) + logCl.00/4.00)What is .the approximate ratio of CH3COO~ toCH3OOH for acetic acid (pKa = 4.8) at pH 4.8?"(A) antilog-1(B) logl(C) 1:1i u\) What is the solubility of CuS at 25°C if itsKsp - 6 X 10~37?(A) 7.4 X 10~i7g/L(B) 3.0 X 10-19g/L(C) 7,4 X 10-19g/LCD) 7.7 X 10-I9g/L(E) 7.7 X 10~38 g/LWhich of the following procedures will produce abuffered solution?I. Equal volumes of I'M NH3 and 1 MNH4C1 solutions are mixed.II. Equal volumes of 1 M H2CO3 and 1 MNaHCO3 solutions are mixed.III. Equal volumes of 1 M NH3 and 1 MH;CO3 solutions are mixed.(A) I only(B) in only(C) 1 and II only(D) n and m only(E) I, H, and IKA 50.0-mL sample of an aqueous H2SO4solution is titrated with a 0.375 M NaOHsolution. The equivalence point is reachedwith 62.5 mL of the base. The concentrationof H2SO4 is(A) 0.234 M(B) 0.469 MCO 0.150 M(D) 0.300 M(E) 0.938 MWhich of the following solid salts is moresoluble in 1.0 M H+ than in pure water?(A)(B)(C)(D)(E)NaClCaCO3KC1AgClKNO3

Equivalence point \.mL NaOHmLNaOHm. IV.mLHClCouid represent the titration curve of HC.jK.jQ(A)!(B)n(D)TV(E) None of the graphs are an accurate representation.^ Could represent the titration of a polyprotic acid(A) I(B)U(C)m(D) IV(E) None of the graphs are an accurate representation.^l^J Could represent the titration of NH,(A)!(B)ii(OruCD) TV(E) None of the graphs are an accurate representation.raLNaOHA chemist creates a buffer solution by mixing equalvolumes of a 0.2-molar HOC1 solution and a 0.2-molar KOC1 solution. Which of the following willoccur when a small amount of KOH is added to thesolution?I. The concentration of undissociated HOC1will increase.II.. The concentration of OClT ions willincrease.III. The concentration of H+ ions willincrease.(A) I only(B) Honly(C) rflonly'(D) I and III only(E) II and III onlyv, A pH 7 buffer solution contains H2CO3 and^ NaHCOy What must the ratio of[NaHC03]/[H2CO3 be in order to maintain thesolution at pH 7? The Ka of H2CO3 is4.3 x 10~7.(A) 43(B) 4.3(C) 0.43(D) 86(E) 1.29

You wish to construct a buffer of pH = 7.0. "Which of the following weak acids (withcorresponding conjugate base) would you select?(A) HC1O2 (chlorous acid) Ka -1.2 x 10~2(B) HF (hydrofluoric acid)Ka = 7.2x10^(C) HOC1 (hypochlorous acid) ^ = 3.5xItT8(D) HCN (hydrocyanic acid) ^ = 4.0 x-lCT10(E) C2H5OH (sthanol) Ka= 1.0 x 1(T25"M.The pH of a 0.125 M solution of a weak base is 10.45. What is the p.K|of this acid? • H(A) 3.5 X 10-"(B) 6.4 X 10'7(C). 2.8 X 10-4(D) 2.3 X 10-3(E) 1.2 X 10-2An initial pH of 13.00, an equivalence point at pH 7.0, and a relativelylong, nearly vertical middle section correspond to a titration curve fora) strong acid titrated by strong baseb) strong base titrated by strong acidc) weak acid titrated by strong acidd) weak base titrated by strong acide) weak base titrated by weak acid0 Which of the following could be added to a solution of acetic acid toprepare a buffer?a) sodium hydroxideb) hydrochloric acidc) nitric acide) none o^lnese'can be added to an acetic acid solution to prepare abuffer/•#, When 0.250 mol of NaOH is added to 1.00 L of 0.100 M HJPO4l the1 ,\ ji •*» •

A solution containing 2.3 X 1(T' molCoCl2 is added to a solution containing1.2 X 10-6molNa2CO3. (K = 1.0 X 10~10for CoCO3.) Which of the followingstatements is true?(A) CoCO3 will precipitate because Q > K5p.(B) CoCO3 will not precipitate becauseQ>Ksp.L(C) CoCO, will precipitate because Q < iC./T^( „ ^^3 .,, . . , 5P(D) CoCO3 will not precipitate becauseQ

11.10. 9:."'"'" 83-79-- 654- 3210Equivalence pointmLNaOHH.mLNaOHm.f,flmLHCICould represent the titration of a polyprotic acid(A) IThe addition of nitric acid increases thesolubility of which-of the followingcompounds ?(C)ffi(D)IV(E) None of the graphs are an accurate representation.Could represent the titration curve of HC,H3Q2(A) I

Io o a\- O o r-l

NGiven the following table of Ksp values, determine which compound listedhas the smallest solubility.compoundCdC03Cd(OH)2AglFe(OH)3ZnC03a) ZnC03b) Cd(OH)2c) CdC03d) Agle) Fe(OH)3The solubility of which onepH of the solution?a) Na3P04b) NaFc) KN03d) A1C13e) MnSKsp5.2 x2.5 x8.3 x4 x 1C1.4 xio-12io-1410-17-3810-1Xof the following will not be affected by theJl'"One liter of solution contains 2.4 X 10~3 mol of sulfate ions. "What is tS|molar solubility of BaSO4 in this solution? (Kso = 1.1 X ICT10 fq§BaS04)'|(A) 1.05 X IO-5fl(B) 1.1 x lO-^ - |(C) 2.6 X 10~i3(D) 2.2 X IO7(E) 4.6 X 10~s, What is the solubility at 25°C of Zn(OH)2 if ^its K =3.0 X 10~16?(A) 8.7 X 10~9 g/L(B) 4.2 X 10~6g/L(Q4.2X 10~4g/L(D)6.7 X 10~6g/L(E) 6.7 X 10"4g/LIn a 1.0 L sample of 0.01 M potassium sulfate,K,SO4 what is the minimum number of molesof calcium chloride, CaCl9, that can be addedto the solution before the precipitate calcium,sulfate forms? Assume that the addition ofcalcium chloride has a negligible effect on thetotal volume of the solution. Ks for CaSO4 -2.4 x IQ-5(A)2.4x IO'5 mol(B)1.2x lQ-3mol(C)2.4x 10-](D)1.2x lO^(E)O.OI molCalculate the maximum concentration (inM) of silver ions (Ag+) in a solution thatcontains 0.025 M of CO2". The Ksp ofAg2CO3is8.1 X 10~12.(A) 1.8 X 10~5M(B) 1.4 X 10~6M(C) 2.8 X 10~6M(D)3.2 X 10~10M(E) 8.1 X !0~12MKC1 is added to a solution that containsequivalent amounts of the following threeions. In what order will the ions precipitateout of solution? For PbCl2>.Ksp - 1.7 X10~5; for Hg2Cl2, K$p = 1.2 X 10~18; andforAgCl,JC = 1.8 X 10-10I. Pb2+II. Hg2.4"III. Ag+(A) I, II, III(B) I, III, II(C) II, III, I(D) II, I, III(E) III, II, I

HOBr(fl?) ^ H+(ag) + OBr(ag) ^ = 2.3 x 1(T9C£ 1Hypobromous acid, HOBr, is a weak acid that dissociates in water, as represented by the equation above.(a) Calculate the value of [H+] in an HOBr solution that has a pH of 4.95.(b) Write the equilibrium constant expression for the ionization of HOBr in water, then calculate theconcentration of HOBr(ntj) in an HOBr solution that has [H+] equal to l,8xlCT5M,(c) A solution of Ba(OH)2 is titrated into a solution of HOBr.v(i) Calculate the volume of 0.115M Ba(OH)2f/z

^.\e graph below shows the result of the titration of a25 mL sampleof aO.10 A/ solution of a weak acid, HA,(6c\j with a strong base, 0.10 M NaOH.10 15 20 25MiUiliters of OJO M NaOH Added30(a) Describe two features of the graph above that identify HA as a weak acid.(b) Describe one method by which the value of the acid-dissociation constant for HA can be determined usingthe graph above.(c) On the graph above, sketch the titration curve that would result if 25 mL of 0.10 M HC1 were used insteadof 0.10 M HA.(d) A 25 mL sample of 0.10 M HA is titrated with 0.20 M NaOH.(1) What volume of base must be added to reach the equivalence point?(ii) The pH at the equivalence point for this titration is slightly higher than the pH at the equivalence pointin the titration using 0.10 M NaOH. Explain.

Answer the following questions that relate to solubility of salts of lead and barium.0s v(a) A saturated solution is prepared by adding excess PbI2(s) to distilled water to form 1 .0 L of solution at25°C. The concentration of Pb2+(aq) in the saturated solution is found to be 1.3 x 10~3 M. The chemicalequation for the dissolution of PbI2(s) in water is shown below.(i) Write the equilibrium-constant expression for the equation.(ii) Calculate the molar concentration of l~(aq) in the solution.(iii) Calculate the value of the equilibrium constant, Jf .(b) A saturated solution is prepared by adding PbI2(j) to distilled water to form 2.0 L of solution at 25°C, Whatare the molar concentrations of Pb2+(ag) and l~(aq) in the solution? Justify your answer.(c) Solid Nal is added to a saturated solution of PbI2 at 25°C. Assuming that the volume of the solution doesnot change, does the molar concentration of Pb2+(a#) in the solution increase, decrease, or remain thesame? Justify your answer.2 l(d) The value of K5 for the salt BaCrO4 is 1 .2 x 1(T10. When a 500. mL sample of 8.2 x 10" 6 M Ba(NO3)2is added to 500. mL of 8.2 x 10~6 M Na2CrO4 , no precipitate is observed.(i) Assuming that volumes are additive, calculate the molar concentrations of Ba2+(a

A student performed a titration of a weak, monoprotic acid, HA, with a sodium hydroxide, NaOH,solution.(a) On the graph that is provided, sketch an approximate representation of the titration curve for theexperiment. On the curve, label the equivalence point.Volume of NaOH (mL)(b) Discuss at least two ways in which the sketch in (a) differs from the plot that would result fromthe titration of a strong, monoprotic, like HC1.(c) The student has a choice between the two indicators: methyl red (pH range 4.8 - 6.0) or phenolphthaiein(pH range - 8.2 - 10.0). Which should she choose? Justify your response.(d) While the student was performing her first trial, she dispensed 50.0 mL of titrant (base) from herburet (the maximum), but her analyte (acid) still had not changed color. What is the most likelysource of her error (assume that she did put an indicator in the anaiyte)?

A solution is prepared by adding 3.0 x 10"4 moles of PbI2 to distilled water to form 500 mlof solution at 25 °C. The K of PbI2 at this tempertature is 1.4 x 10~3.a) Explain why this solution is not saturated using the solubility product constant and theion product.b) Nal is slowly added to the solution. How many moles of Nal must we add to induceprecipitation'of PbI2?A 0.20-molar solution of acetic acid, HC2H3O2, at a temperature of 25°C, has a pH of 2.73.(a)(b)(c)(d)Calculate the hydroxide ion concentration, [OH"].What is the value of the acid ionization constant, Ka, for acetic acid at 25°C?How many moles of sodium acetate must be added to 500. ml of a Q.200-molar solution of acetic acid in orde:to create a buffer with a pH of 4.00? Assume that the volume of the solution is not changed by the addition osodium acetate.In a titration experiment, 100. ml of sodium hydroxide solution was added to 200 ml of a 0.400-molaxsolution of acetic acid until the equivalence point was reached. What was the pH at the equivalence point?

,. , The solubility of calcium oxalate, CaC2O4, is 6.1 x Ifr3 g per liter at 25 °C. j(H-i I1 7 (a) Determine the molar solubility of CaC204 at 25 DC. i(b) Write a balanced equation for the solubility equilibrium.(c) Wri-.r he expression for the solubility product constant, K , and calculate its value.(d) If CaC,04 is placed in a 0.10 M CaCl2 solution, bow will this affect the molar solubility?Explain, and show calculations to support your answer.(e) If 50.0 mL of 0.0025 M CaCl3 is added to 50.'.:• mL of 1.0 x 105 M Na3C2O4, will any calciumoxalate precipitate?A 100. zrulljliter sample of Q.lOO-molar N_i4Cl solution was added to 80 mill 'liters of a 0.200-molarsolution of NHj. The value of Kfr for ammonia is 1-.79 X lO"5.(a)(b)(c)(d)What is the value of pKb for ammcnia?What is the pH of the solution described in the question?If 0.200 granis of NaOH were adcad to the solution, what would be the new pH of the solution?(Assume that the volume of the solution does not change.)If equal molar quantities of NHg and NH4* were mixed in solution, what would be the pH ofthe solution?

BaF:(s) ^ Ba:*(^) + 2 F-(fl£?)The value of the solubility product, K, for the reaction above is 1.0 x 10"* at 253C.(a)(b)Write the K expression for BaFrWhat is the concentration of F~ ions in a saturated solution of BaF2 at 25QC?(c) 500 inmters of a 0.0060-molar NaP solution is added to 400 ml of a 0.0060-solution. Will there be a precipitate?) A beaker contains 100 rrtOliliters of a solution of hypochlorous acid, HOCI, of unknown concentration.(a)(b)(c)(a)The solution was titrated with 0.100 molar NaOH solution and the equivalence point wasreached when 40.0 rnilliliters of NaOH solution was added. What was the original concentrationof the HOCI solution?If the original HOCI solution had a pH of 4.46, what is the value of Ka for HOCI?What percent of the HOCI molecules were ionized in the original solution?What is the concentration, of OC1" ions in ihe solution at the equivalence point reached in (a)?

A saturated solution of magnesium hydroxide, Mg(OH)2, has a magnesium ion concentrationof 1.65 x IQ^1 M at 25°C.(A) What is the value of the solubility product constant, K , at 25°C?sp(B) What is the molar solubility of Mg(OH)7 in 0.10 M Mg(NO,J, solution at 25°C?(C) To 350. ml of a 0.150 M Mg(NO3)2 solution, 150. mL of a 0.500 M NaOH solutionis added. What are the [Mg2+] and [OH~] in the resulting solution at 25°C?(D) If the temperature were raised to 50°C, what effect will this change have on solubilityproduct constant, K ? Explain briefly.A 50.00 mL sample of 0.25 M benzole acid, RCfL$Oy is titrated with 0.199M NaOH solution. The K of benzole acid is 6.3 x 10'5.a(a) What is the pH, pOH, and [H^O*] of the benzole acid solution prior tothe titration?(b) How many miliiliters of NaOH are required to reach the equivalencepoint?r(c) What is the pH of the solution at the equivalence point?(d) Which of the following would be the best indicator to use for thistitration?Methyl redCresolred£o=lxlO-5/ = 1x10-*Alizarin yellow Ka = I x 10'11Justify your response.

a) Magnesium metal and a lithium sulfate solution are mixedb) Solutions of oxalic acid and calcium hydroxide are mixedc) Aqueous potassium oxide and aqueous nitric acid are combinedd) Liquid 2-pentanone is burned in aire) Solid iron(II) carbonate decomposesf) Gaseous carbon dioxide is bubbled through aqueous sodium hydroxideg) A 30% hydrogen peroxide solution decomposesh) Gaseous nitrogen dioxide is bubbled through liquid wateri) Solid lithium is dropped in liquid waterj) Ethanal undergoes combustionk) Solutions of iron(III) nitrate and ammonia react