Chem Exam 3

Calculate pBa when 75.00 mL 0.1 M EDTA is added to 50.00 mL of 0.1 M Ba2+. For the buffered pH of 10, = 0.30. Kf = 7.59 × 107 for BaY2-. a. 7.06 b. 3.53 c. 4.33 d. 7.58 e. 4.59

a

In which solution is solubility of silver chloride the largest? a. Pure water b. 0.05 M CaCl2 c. 0.10 M NaCl d. 0.10 M FeCl3 e. 0.15 M AgNO3

a

Nickel forms three complexes with hydroxide, NiOH+ (aq), Ni(OH)2 (aq) and Ni(OH (aq). Which statement(s) regarding the impact of complex formation on the solubility of nickel hydroxide are FALSE? ​ I Hydroxide behaves as a Lewis acid when forming a complex with nickel. II The total nickel concentration is [Ni2+]tot = [Ni2+] + [NiOH+] + [Ni(OH)2] + [Ni(OH]. III As [OH-] increases, the solubility of Ni(OH)2 initially decreases but then increases. IV B3= [Ni(OH)3-]/[Ni2+][OH-]3 a. Only I b. II and III c. Only III d. Only IV e. I, II, III, and IV

a

The key step to titration calculations is to relate: a. moles titrant to moles analyte. b. volume titrant to volume analyte. c. grams titrant to grams analyte. d. conductivity titrant to conductivity analyte. e. reduction titrant to oxidation analyte.

a

Which statements below are TRUE for enthalpy and entropy? ​ I Enthalpy is the heat flow, q, under constant applied pressure. II Standard conditions for entropy and enthalpy changes are 1 M concentration, 1 bar pressure and 298.15 K. III The entropy change for a system is the amount of energy, at a given temperature, that is dispersed into motion of the molecules in the system. IV When the value of H is negative, heat is released. When the value of S is negative, entropy is increased. a. I, II and III b. I, III and IV c. II and IV d. III and IV e. Another combination is true.

a

A compound available in high purity, does not decompose under ordinary storage conditions and stable while being dried by heating or vacuum is a: a. secondary standard. b. primary standard. c. standard solution. d. indicator. e. titrant.

b

A metal that does not freely dissociate from an indicator is said to ___________ the indicator. a. hinder b. block c. restrict d. impair e. handicap

b

A student attempts to separate Cl- and I- from a solution that is 0.05 M Cl- and 0.10 M I- with Pb(NO3)2. As Pb(NO3)2 is added, which anion will precipitate first and what will the concentration of the anion be when the second anion begins to precipitate? Ksp = 1.7 x 10-5 for PbCl2 and Ksp = 9.8 x 10-9 for PbI2. a. iodide precipitates first; 0.0068 M iodide b. iodide precipitates first; 0.0012 M iodide c. iodide precipitates first; 0.05 M iodide d. chloride precipitates first; 0.0012 chloride e. chloride precipitates first; 0.10 M chloride

b

Argentometric titrations are titrations using: a. Au+. b. Ag+. c. Ar+. d. Al3+. e. As3-.

b

Calculate pBa when 35.00 mL 0.1 M EDTA is added to 50.00 mL of 0.1 M Ba2+. For the buffered pH of 10, = 0.30. Kf = 7.59 × 107 for BaY2-. a. 1.39 b. 1.75 c. 4.56 d. 4.82 e. 4.70

b

Calculate pBa when 35.00 mL of 0.1 M EDTA is added to 50.00 mL of 0.1 M Ba2+ in the presence of 0.1 M nitrilotriacetate. = 1.48 × 10-4. = 0.30 for pH 10. Kf = 7.59 × 107 for BaY2-. a. 4.82 b. 2.64 c. 1.75 d. 4.55 e. 3.53

b

For the reaction HCN (aq) + H2O (l) CN- (aq) + H3O+ (aq), all of the following will shift the equilibrium toward the products, except: ​ I adding HCN. II adding H2O. III removing CN-. IV removing H3O+. a. I b. II c. I, III, and IV d. II and IV e. III

b

What is the pH for a 5 x 10-5 M OH- solution? a. 5.70 b. 4.30 c. 9.70 d. 5.00 e. 9.00

b

Which is NOT an end point detection method used with EDTA titrations? a. metal ion indicators b. adsorption indicators c. glass (pH) electrode d. mercury electrode e. ion-selective electrode

b

Which statement is NOT true? a. A monodentate ligand binds to a metal atom through only one atom. b. A metal is multidentate if it can bind to more than one ligand. c. Metal ions are Lewis acids. d. Ligands are Lewis bases. e. Most transition metals bind six ligand atoms.

b

A ____________ is a reagent that protects a component of the analyte from reaction with EDTA. a. hindrance agent b. displacement agent c. masking agent d. blocking agent e. reducing agent

c

For a reaction with a Ho = +50 kJ and a So = +100.0 J/K, Go is _______________ and the equilibrium constant is _______________. a. negative; less than 1 b. negative; greater than 1 c. positive; less than 1 d. positive; greater than 1 e. zero; 1

c

For a triprotic acid, which of the following is NOT true? a. Ka1Kb3=Kw b. Ka2= [H+][HA-]/[H2A-] c. Ka1Kb2=Kw d. Ka3Kb1=Kw e. Kb1= [HA2-][OH-]/[A3-]

c

The ____________ is the ability of multidentate ligands to form more stable metal complexes than those formed by similar monodentate ligands. a. ligand effect b. multidentate effect c. chelate effect d. Lewis effect e. isomer effect

c

Which of the following terms is INCORRECTLY defined? a. titration error: the difference between the end point and the equivalent point b. direct titration: titrant is added to analyte until reaction is complete c. equivalent point: volume of titrant added in excess of the end point to change a physical property of the analyte solution d. blank titration: titration performed without analyte to calculate titration error e. standardization: titration of a known amount of analyte to determine the concentration of the titrant

c

A Na2CO3 standard solution is prepared by transferring 2.4817 grams of primary standard-grade sodium carbonate to a 250.0-mL volumetric flask, dissolving the sample in ~100 mL of distilled deionized water and diluted to the mark. A 25.00-mL aliquot is taken and titrated with 42.65 mL of HCl solution. Calculate the concentration of the HCl solution. a. 0.05490 M b. 0.1598 M c. 0.3196 M d. 0.1098 M e. 0.1997 M

d

A(n) _________________ is a compound with a physical property that changes abruptly near the equivalence point. a. primary standard b. titrant c. analyte d. indicator e. masking agent

d

Common _______________- indicators are anionic dyes that are attracted to positively charged particles produced immediately after the equivalence point. a. redox b. absorption c. acid-base d. adsorption e. complexometric

d

For EDTA titrations the titration reaction is Mn+ + EDTA MYn-4. Which statements are true for EDTA titration curves? I At the equivalence point, there is exactly as much EDTA in solution as metal. [Mn+] is calculated from the dissociation of MYn-4 formed. II After the equivalence point, the concentration free EDTA equals excess EDTA and virtually all metal ion is in the form MYn-4. [Mn+] is calculated from the dissociation of MYn-4. III Before the equivalence point, free [Mn+] equals excess unreacted Mn+ after EDTA has been consumed. Dissociation of MYn-4 is negligible. IV pM is plotted on the y-axis and milliliters EDTA solution added on the x-axis. a. I, II, and III b. I, III, and IV c. III and IV d. I, II, III, and IV e. II, III, and IV

d

For the reaction aA (aq) + bB (s) cC (l) + dD (g), all of the statements below are TRUE, except: a.K= (Pd)^d/[A]^a b. concentrations of solutes are expressed in moles per liter. c. concentrations of gases are expressed in bars. d. concentrations of pure solids, pure liquids and solvents are omitted because they are negligible. e. quantities in the equilibrium expression are the ratio of the concentration of the species to the concentration in its standard state.

d

The end point for the Volhard titration is indicated by: a. adsorption of a colored indicator on the precipitate at the end point. b. reduction of a colored indicator at the end point. c. deprotonation of a colored acid-base indicator at the end point. d. formation of a soluble, colored complex at the end point. e. protonation of a soluble, colored complex at the end point.

d

The pH of a solution is 9.65. The solution is ____________________ and the hydroxide concentration is _________________ than the hydronium concentration. a. acidic; less b. acidic; greater c. neutral; equal d. basic; greater e. basic; less

d

When the direction for a reaction is reversed the new value of K is: a. K = log(K). b. K = ln(K). c. K = 10K. d. K = 1/K. e. K = eK.

d

Which statement is NOT true for auxiliary complexing agents? a. Auxiliary complexing agents prevent the precipitation of metal hydroxide at high pH. b. Auxiliary complexing agents are chosen to bind metal strong enough to prevent metal hydroxide precipitation but weak enough to be displaced by EDTA. c. is the effective formation constant for fixed pH and fixed concentration auxiliary complexing agent. d. Low concentrations auxiliary complexing agent obliterates the end point of the titration. e.

d

Which statement is incorrect for conditional formation constants, Kf ? a. Kf is pH dependent. b. Kf = Y4- Kf c. Kf allows the view of uncomplexed EDTA as being in only one form, Y4-, in equilibrium calculations. d. As pH drops the value of Kf increases. e. The values of Kf must be large to guarantee sharp end points during titrations.

d

A _____________ titration is necessary for analytes that precipitates in the absence of EDTA, that reacts slowly with EDTA or that blocks the indicator. a. direct b. displacement c. indirect d. masking e. back

e

All of the following are strong acids, except: a. HCl. b. HNO3. c. HBr. d. HClO4. e. HF.

e

Calculate pBa when 50.00 mL 0.1 M EDTA is added to 50.00 mL of 0.1 M Ba2+. For the buffered pH of 10, = 0.30. Kf = 7.59 × 107 for BaY2-. a. 1.30 b. 7.88 c. 4.59 d. 7.36 e. 4.33

e

EDTA is a hexadentate ligand containing four carboxylic acid groups and two amines. Which is true for the acid-base properties of EDTA? I EDTA is a hexaprotic system, H6Y2+, when the amines are protonated. II Neutral EDTA, H4Y, is tetraprotic when the amines are not protonated. III Deprotonated EDTA, Y4-, is the only form of EDTA that binds to metal cations. IV The fraction of EDTA in any of the six EDTA species is pH dependent. a. III and IV b. I and II c. I, III, and IV d. II, III, and IV e. I, II, and IV

e

The molar solubility of a saturated iron(II) carbonate solution derived from the Ksp value is 5.6 x 10-6 M. The molar solubility is greater than 5.6 x 10-6 M when accounting for additional reactions. Which of the reactions below will not increase the solubility of iron(II) carbonate? a. Fe2+ (aq) + OH- (aq) FeOH+ (aq) b. CO32- (aq) + H+ (aq) HCO3- (aq) c. HCO3- (aq) + H+ (aq) H2 CO3 (aq) d. H2CO3 (aq) CO2 (g) + H2O (l) e. FeOH+ (aq) + OH- Fe(OH)2 (s)

e

Which of the classes of acids and bases and strength have been incorrectly matched? a. RCO2H: weak acid b. R3N: weak base c. RCO2-: weak base d. R3NH+: weak acid e. R4NOH: weak base

e

Which of the following is INCORRECT for Brønsted-Lowry acids and bases? a. Acids are proton donors. b. NH4+ is the conjugate acid of the weak base NH3. c. When an acid and a base react, the acid and base neutralize each other and form a salt. d. Water reacts with itself to form hydronium and hydroxide, a process called autoprotolysis. e. CH3CN is a protic solvent.

e