Deck 13: Edta Titrations

Question 1

The reaction between Al³⁺ and EDTA is too slow for direct titration.To a 25.00 mL Al³⁺ sample 50.00 mL of 0.2000 M EDTA is added and allowed to react for 30 minutes.The excess EDTA was titrated with 21.23 mL of 0.1000 M Zn²⁺.What is the concentration of Al³⁺ in the sample?

Answer 1

0.3151 M Al³⁺

Question 2

Calculate [Ba²⁺] when 35.00 mL of 0.2000 M EDTA is added to 50.00 mL of 0.1000 M Ba²⁺ in the presence of 0.1 M nitrilotriacetate. = 1.48 x 10⁻⁴. = 0.30 for pH 10.K_f = 7.59 × 10⁷ for BaY²⁻.

Answer 2

7.424 × 10⁻⁴ M Mn²⁺

Question 3

Calculate [Mn²⁺] when 50.00 mL of 0.1000 M Mn²⁺ is titrated with 17.00 mL of 0.2000 M EDTA.The titration is buffered to pH 11 for which = 0.81.K_f = 7.76 × 10¹³

Answer 3

0.02388 M Mn²⁺

Question 4

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)

Question 5

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.K_f = 7.59 × 10⁷ for BaY²⁻.

A)4)82
B)2)64
C)1)75
D)4)55
E)3)53

Question 6

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

Question 7

Ammonia,0.10 M,is used as an auxiliary complexing agent for a Co²⁺ titration with EDTA.There are 6 $\beta$ s for the complex between ammonia and Co²⁺.Which equation is used to calculate ?

A)
B)
C)
D)
E)

Question 8

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

Question 9

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

Question 10

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.K_f = 7.59 × 10⁷ for BaY²⁻.

A)1)39
B)1)75
C)4)56
D)4)82
E)4)70

Question 11

For EDTA titrations the titration reaction is Mⁿ⁺ + EDTA ⇋ MY^n-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 MY^n-4 formed.
II After the equivalence point,the concentration free EDTA equals excess EDTA and virtually all metal ion is in the form MY^n-4.[Mⁿ⁺] is calculated from the dissociation of MY^n-4.
III Before the equivalence point,free [Mⁿ⁺] equals excess unreacted Mⁿ⁺ after EDTA has been consumed.Dissociation of MY^n-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

Question 12

Calculate [Mn²⁺] when 50.00 mL of 0.1000 M Mn²⁺ is titrated with 25.00 mL of 0.2000 M EDTA.The titration is buffered to pH 11 for which = 0.81.K_f = 7.76 × 10¹³

Question 13

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.

Question 14

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

Question 15

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.K_f = 7.59 × 10⁷ for BaY²⁻.

A)1)30
B)7)88
C)4)59
D)7)36
E)4)33

Question 16

Calculate for a 0.2 M EDTA solution buffered at pH 10.00.For EDTA K₁ = 1.0,K₂ = 31.6,K₃ = 100,K₄ = 490,K₅ = 1.35 × 10⁶ and K₆ = 2.34 × 10¹⁰.

Question 17

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

Question 18

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.K_f = 7.59 × 10⁷ for BaY²⁻.

A)7)06
B)3)53
C)4)33
D)7)58
E)4)59

Question 19

Which statement is incorrect for conditional formation constants,K_f^′?

A)K_f^′ is pH dependent.
B)K_f^′
C)K_f^′ allows the view of uncomplexed EDTA as being in only one form,Y⁴⁻,in equilibrium calculations.
D)As pH drops the value of K_f^′ increases.
E)The values of K_f^′ must be large to guarantee sharp end points during titrations.

Question 20

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