the experiment of qualitative analysis of cations
Experiment # 8
Qualitative Analysis of Cations
Objectives
Part I: Separate a mixture of known cations: Pb2+, Fe3+, Al3+, Cu2+, and Ca2+ into individual ions. Perform a series of tests to become familiar with reactions characteristic of each cation.
Part II: Separate and identify individual cations in an unknown solution containing a mixture of up to five cations. Use information gathered in part I to identify the cations.
Introduction
Qualitative analysis is a general name for the process of determining the identity rather than the amount of chemical species. The qualitative process utilizes reaction(s) characteristic of a given chemical species and interprets the obtained results using a deductive thought process. Qualitative analysis of cations requires an extensive knowledge of various aspects of chemistry including acid-base equilibria, complex ion equilibria, solubility, etc. However, in the deductive process, common sense and logic can be as helpful as a knowledge of the chemistry involved.
In this lab you will be working with a solution containing a mixture of cations.
Before individual components of the mixture can be successfully identified, they have to be separated. The individual cations, once separated, can then be identified in ensuing confirmatory reactions (see the flowchart below). Knowing the actual results of the reactions characteristic for a given cation (or a group of cations) makes it easier to identify the ion in an unknown sample. Therefore, it is useful to perform all of the characteristic reactions first on a mixture of ions of known identity, and then proceed to the unknown sample.
Reactions Characteristic for Pb+2
Separation of Pb+2 from Fe+3, Al+3, Cu+2, and Ca+2
Out the five cations in the mixture, only lead ion will precipitate, as PbCl2, when hydrochloric acid is added to the solution.
Pb2+ (aq) + 2Cl- (aq)
PbCl2 (s,white)
Equation 1
The solid PbCl2 is separated from the solution containing the
Qualitative Analysis of Cations
Objectives
Part I: Separate a mixture of known cations: Pb2+, Fe3+, Al3+, Cu2+, and Ca2+ into individual ions. Perform a series of tests to become familiar with reactions characteristic of each cation.
Part II: Separate and identify individual cations in an unknown solution containing a mixture of up to five cations. Use information gathered in part I to identify the cations.
Introduction
Qualitative analysis is a general name for the process of determining the identity rather than the amount of chemical species. The qualitative process utilizes reaction(s) characteristic of a given chemical species and interprets the obtained results using a deductive thought process. Qualitative analysis of cations requires an extensive knowledge of various aspects of chemistry including acid-base equilibria, complex ion equilibria, solubility, etc. However, in the deductive process, common sense and logic can be as helpful as a knowledge of the chemistry involved.
In this lab you will be working with a solution containing a mixture of cations.
Before individual components of the mixture can be successfully identified, they have to be separated. The individual cations, once separated, can then be identified in ensuing confirmatory reactions (see the flowchart below). Knowing the actual results of the reactions characteristic for a given cation (or a group of cations) makes it easier to identify the ion in an unknown sample. Therefore, it is useful to perform all of the characteristic reactions first on a mixture of ions of known identity, and then proceed to the unknown sample.
Reactions Characteristic for Pb+2
Separation of Pb+2 from Fe+3, Al+3, Cu+2, and Ca+2
Out the five cations in the mixture, only lead ion will precipitate, as PbCl2, when hydrochloric acid is added to the solution.
Pb2+ (aq) + 2Cl- (aq)
PbCl2 (s,white)
Equation 1
The solid PbCl2 is separated from the solution containing the