EDTA Titrations: Introduction to Metal Chelate Complexes

What is a characteristic of a reagent used in a titration?

It reacts with an analyte in a variable ratio
It reacts with an analyte in a known ratio (correct)
It has a small equilibrium constant
It is not a Lewis acid or base

What is the term for the reaction of a metal ion with a chemical agent to form a complex?

Lewis Acid-Base Reaction
Complexation Reaction (correct)
Redox Reaction
Chelation Reaction

What is the role of the metal in a metal-ligand complex?

Lewis Base
Catalyst
Electron-pair donor
Electron-pair acceptor (correct)

What is the term for the ligands used in complexometric titrations?

Chelating Agents (C) Signup and view all the answers

What type of reaction is involved in complexation titrations?

Lewis Acid-Base Reaction (C) Signup and view all the answers

What is the nature of the titration of a metal ion with EDTA?

Strong acid with a weak base (D) Signup and view all the answers

What is the number of distinct regions in an EDTA titration curve?

3 (C) Signup and view all the answers

What is the relation between pM and [Mn+]?

pM is equal to the negative logarithm of [Mn+] (B) Signup and view all the answers

What is the value of Ve at the equivalence point?

50.0 mL (D) Signup and view all the answers

What is the condition before the equivalence point in an EDTA titration?

Excess Mn+ (D) Signup and view all the answers

What is the assumption made about the dissociation of MYn-4 before the equivalence point?

It is negligible (B) Signup and view all the answers

What is the concentration of excess EDTA after the equivalence point?

4.95 × 10^−4 M (B) Signup and view all the answers

What is the concentration of MgY2- after the equivalence point?

0.0248 M (D) Signup and view all the answers

What is the value of Kf in the equilibrium expression for Mg2+ and EDTA?

6.2 × 10^4 (B) Signup and view all the answers

What is the concentration of Mg2+ after the equivalence point?

2.7 × 10^−7 M (C) Signup and view all the answers

Why is the equivalence point sharper for Zn2+ compared to Mg2+?

Due to the larger formation constant of Zn2+ (D) Signup and view all the answers

What is the term that describes the completeness of the reaction between Mg2+ and EDTA?

aY4- (B) Signup and view all the answers

What is the effect of increasing pH on the Kf of a metal ion with EDTA?

Kf increases (B) Signup and view all the answers

What is the purpose of adding an auxiliary complexing agent in EDTA titration?

To prevent the formation of an insoluble metal hydroxide (C) Signup and view all the answers

What is the effect of adding ammonia buffer to a CuSO4 solution?

It forms a dark blue solution (B) Signup and view all the answers

What happens when EDTA is added to a Cu-ammonia complex?

The ammonia is displaced with a corresponding color change (D) Signup and view all the answers

What is the purpose of a conditional formation constant in EDTA titration?

To incorporate the fraction of free metal ion (D) Signup and view all the answers

How many methods are there to determine the end point of an EDTA titration?

4 (A) Signup and view all the answers

What is the purpose of adding an auxiliary complexing agent in direct titrations?

To prevent precipitation of metal hydroxide (C) Signup and view all the answers

In back titrations, what is done with the remaining excess of EDTA?

It is titrated with a standard solution of a second metal ion (C) Signup and view all the answers

What is the condition required for a displacement titration to work?

Kf(analyte) > Kf(second metal ion) (A) Signup and view all the answers

What is the purpose of using Mg(EDTA)2- in displacement titrations?

To release Mg2+ ions (A) Signup and view all the answers

What is the advantage of indirect titrations?

They can be used to determine anions that precipitate with metal ions (A) Signup and view all the answers

What is the relationship between the amount of Mg2+ released and the concentration of Mn+ in displacement titrations?

The amount of Mg2+ released is equal to the concentration of Mn+ (D) Signup and view all the answers