CHEM005 Final 2023 with verified questions and answers

Fumaric acid has two conjugate base forms, with pKa1=3.02 and pKa2=4.48, at what pH value αHA- got its largest fractions? a. 3.02 b. 4.48 c. 3.75 d. 5.41 c. 3.75 For a diprotic system, the equation for the fraction of A2-(αA2-) is a. αA2- = K1K2/([H+]2+[H+]K1+K1K2) b. αA2- = [H+]2/([H+]2+[H+]K1+K1K2) c. αA2- = K1K2/([H+]+[H+]K1+K1K2) d. αA2- = [H+]2/([H+]+[H+]K1+K1K2) a. αA2- = K1K2/([H+]2+[H+]K1+K1K2) A 25.00mL solution of 0.0316M benzylamine was titratd with 0.02M HCl. How many HCl was consumed at equivalence point? a. 31.90mL b. 38.88mL c. 39.50mL d. 63.80mL c. 39.50mL 40.0mL of 0.100M piperazine was titrated with 0.100M HCl. Piperazine has pKa1=5.33 and pKa2=9.73. What is the pH value when 25mL of HCl was added? e. 9.73 f. 9.51 g. 5.33 h. 4.86 f. 9.51 A 200.0mL aliquot of 0.100M diprotic acid H2A (pK1=3.00, pK2=7.00) was titrated with 1.00M NaOH. How much NaOH is added when solution pH=5.00? a. 10mL b. 20mL c. 30mL d. 40mL b. 20mL For diprotic acid H2A, Ka1=1.00x10-4, Ka2=1.00x10-8. What is the pH for 0.100 M H2A? a. 2.51 b. 2.79 c. 3.33 d. 4.26 a. 2.51 Which EDTA species predominates in a medium pH 11.0? a. H3Yb. HY3- c. H2Y2- d. Y4- d. Y4- Write a charge balance for a solution containing H+, OH-, Ca2+, HCO3-, CO32-, Ca(HCO3)+,Ca(OH)+, K+, and ClO4-. a. [H+] + [Ca2+] + [K+] = [OH-] + 2 [CO32-] b. [H+] + [Ca2+] + [Ca(HCO3)+] + [Ca(OH)+] + [K+] = [ClO4-]+[OH-] + [HCO3-] +[CO32-] c. [H+] + 2[Ca2+] + [Ca(HCO3)+] + [Ca(OH)+] + [K+] = [ClO4-] + [OH-] + [HCO3-] +2[CO32-] d. [ClO4-] + [H+] + 2[Ca2+] + [Ca(HCO3)+] + [Ca(OH)+] = [OH-] + [HCO3-] +2[CO32-] + [K+] c. [H+] + 2[Ca2+] + [Ca(HCO3)+] + [Ca(OH)+] + [K+] = [ClO4-] + [OH-] + [HCO3-] +2[CO32-] For diprotic acid H2A, Ka1=1.00x10-4, Ka2=1.00x10-8. What is the pH for 0.200 M NaHA? a. pH=6.0 b. pH=5.6 c. pH=6.8 d. pH=7.2 a. pH=6.0 The equilibrium constant expression for Ka2 of EDTA (dissociation of H3Y-) can be expressed as a) [H+][H2Y2-]/ [H3Y-] b) [H3Y-] /([H+][H2Y2-]) c) [H+]/ ([H3Y-][H2Y2-]) d) [H3Y-] [H2Y2-] / [H+] a) [H+][H2Y2-]/ [H3Y-] Given the reaction equation metal M forming complex with ligand Y, Mn+ + Y4- → MYn-4, the stability constant Kf is a. Kf = [Mn+][Y4-] /[MYn-4] b. Kf = [MYn-4]/[Mn+][Y4-] c. Kf = [MYn-4]/[Mn+]n[Y4-]4 d. Kf = [Mn+]n[Y4-]4 /[MYn-4] b. Kf = [MYn-4]/[Mn+][Y4-] Write the mass-balance expression for a solution that is saturated with BaC2O4. (a) [Ba2+] = [C2O42-] + [HC2O4-] + 2[H2C2O4] (b) [Ba2+] = [C2O42-] + [HC2O4-] + [H2C2O4] (c) [Ba2+] = [C2O42-] + [HC2O4-] + ½ [H2C2O4] (d) [Ba2+] = 2[C2O42-] + [HC2O4-] + [H2C2O4] (b) [Ba2+] = [C2O42-] + [HC2O4-] + [H2C2O4] If the reaction 2H+ + Cd(s) = H2 (g) + Cd2+ proceeds to the right direction spontaneously, which of the following statements is correct? (a) Oxidizing agents are Cd2+ and H+, and the oxidizing potency: H+ Cd2+ (b) Oxidizing agents are Cd2+ and H+, and the oxidizing potency: Cd2+ H+ (c) Reducing agents are Cd(s) and H2, and the reducing potency: Cd(s) H2 (d) Oxidizing agents are Cd2+ and H2, and the oxidizing potency: Cd2+ H2 (b) Oxidizing agents are Cd2+ and H+, and the oxidizing potency: Cd2+ H+ For the redox reaction of Fe3+ + Sn2+ = Fe2+ + Sn4+, a) Fe3+ is oxidized. b) Sn2+ is reduced. c) Sn2+ is a reducing agent. d) Fe3+ is a reducing agent. c) Sn2+ is a reducing agent. The balance reaction for IO3- with I- to form I2 is: (a) IO3- + I- I2 + H2O (b) IO3- + I- + 6H+ I2 + 3H2O (c) IO3- + 5I- + 6H+ 3I2 + 3H2O (d) IO3- + 3I- + 6H+ 2I2 + 3H2O (c) IO3- + 5I- + 6H+ 3I2 + 3H2O In the reaction Fe3+ + V2+ → Fe2+ + V3+, which of the following is true? a. Fe3+ is oxidized. b. V2+ is an oxidant. c. V2+ takes electrons from Fe3+ in the reaction. d. None is correct. d. None is correct. For the reaction 5Ce4+ + Mn2+ + 4H2O → 5Ce3+ + MnO4- + 8H+, given E0(Ce4+/Ce3+)= 1.70V, E0(MnO4-/Mn2+) = 1.507V, calculate ΔG0 for this reaction ? a. -93.1 kJ b. 93.1 kJ c. 18.6 kJ d. -18.6 kJ a. -93.1 kJ Find the voltage of a cell if the right half-cell contains 0.50 M AgNO3(aq) (E0 = 0.79V) and the left half-cell contains 0.010 M Cd(NO3)2(aq) (E0 = -0.42V). Determine if the cell is spontaneous in the forward or reverse direction. a. Spontaneous in the forward and reverse direction b. Spontaneous in the reverse direction c. Spontaneous in the forward direction d. Nonspontaneous in the forward and reverse direction c. Spontaneous in the forward direction For redox couples: Eo Cl2/Cl-=1.359 V, Eo Ag+/Ag=0.799V, Eo Cu2+/Cu =0.337V, Eo Zn2+/Zn= -0.763V, the order of increasing oxidant strength is a) ZnCuAgCl2 b) Zn2+Ag+Cu2+Cl- c) Zn2+Cu2+Ag+Cl- d) Zn2+Cu2+Ag+Cl2 d) Zn2+Cu2+Ag+Cl2 What is the Nernst equation for the reduction of white phosphorus to phosphine gas: ¼P4(s, white) + 3H+ + 3e-- PH3(g) (E° = -0.046 V) a. E = -0.046 - (0.0592/3)log([PH3]/[H+]3) b. E = -0.046 - (0.0592/2)log([PH3]/[H+]3) c. E = -0.046 - (0.0592/3)log([H+]3/[PH3]) d. E = -0.046 - (0.0592/2)log([H+]3/[PH3]) a. E = -0.046 - (0.0592/3)log([PH3]/[H+]3) Determine the equilibrium constant at 25°C for the titration reaction: Fe2+ + Ce4+ - Fe3+ + Ce3+. The standard electrochemical potential, E°, for this reaction is +0.93 V. a. 5.3×10^15 b. 3.4×10^31 c. 2.7×10^11 d. 8.2×10^6 a. 5.3×10^15 Given the E0 of the following metal ions: E0 (Li+) = -3.045V, E0 (Na+) = -2.714V, E0 (K+) = -2.936V, E0 (Rb+) = -2.925V, which one is the most easily oxidized? a. Li b. Na c. K+ d. Rb+ a. Li Potassium iodate solution was prepared by dissolving 10.22g of KIO3 (FM 214.00) in a 500 mL volumetric flask. Then 50.00mL of the solution was pipetted into a flask and treated with KI (1g) and acid (10mL of 0.5M H2SO4). How many moles of I3- are created by the reaction? a. 4.78 mmol b. 0.985 mmol c. 2.26 mmol d. 7.88 mmol c. 2.26 mmol For reactions: Fe3+ + e = Fe2+ E0 = 0.771V MnO4- + 8H+ + 5e = Mn2+ + 4H2O E0 = 1.51 V. Which of the following is correct? a) The reaction between Fe2+ and MnO4- is spontaneous. b) The reaction between Fe3+ and MnO4- is spontaneous. c) The reaction between Fe3+ and Mn2+ is spontaneous. d) The reaction between Fe2+ and Mn2+ is spontaneous. a) The reaction between Fe2+ and MnO4- is spontaneous. If a redox reaction is at equilibrium at 25 degreesC, then a. Eocell 0 b. Eo cell =0 c. E cell =0 d. Eo cell= -0.0592/n log Keq c. E cell =0 Given the conditional formation constant Kf'=4.1 x 1010, what is the concentration of Mn+ when 60.00mL 0.0500M EDTA was used to titrate 50.0mL 0.0500M Mn+ solution? a. 2.4 x10^-10 M b. 1.2 x10^-10 M c. 4.8 x10^-10 M d. 6.4 x10^-10 M b. 1.2 x10^-10 M Calculate the molar Y4- concentration in a 0.0350 M EDTA solution buffered to pH of 11.00. At pH 11.00 α4 is 0.85. 2.98 × 10^-2 7.23 × 10^-3 3.41 × 10^-8 4.27 × 10^-4 2.98 × 10^-2 "R" Gas Constant R is 8.314 J / mol. K Power Eqn. "P" (J/s)= P= Work/s = Eq/s = E(q/s) Current "I"= I=E/R (resistance in Ohms) deltaG= deltaG= -work = -E*q = -nFE 1 V = = 1 J/C Work= Work= E (volts) * q (Coulombs) 1 Amp = 1 Amp = 1 C/s q = (rate of the reaction) q = n (moles of e-) * F (C/mol e-) Halfway point in H2A titration pH= 1/2(pK1+pK2) deltaG = (using with Ksp) deltaG = (0.0592/n)*log Ksp Which can be defined as quantitative analysis? Determine the amount of contaminates in water samples using HPLC, based on peak area and calibration curve. Absorbance "A" = A= Ebc; E (L/mol*cm), b (cm), c (mol/L) Absorbance "A" = A = -Log (1/T) Transmittance "T" = T = I/Io H3PO4 is a triprotic acid, with pK1=2.148, pK2=7.198, pK3=12.375. Which of the following groups would be chosen to prepare a buffer of pH 7.45? c. H2PO4- and HPO42-