Chemistry Laboratory XII

Theoretical Principles in Qualitative Analysis (H₂S Scheme)

Basic principles involved in analysis of cations and anions and solubility products, common ion effect, principles involved in separation of cations into groups and choice of group reagents, interfering anions (fluoride, borate, oxalate and phosphate) and need to remove them after group II.

Qualitative semi-micro analysis of mixtures containing 3 anions and 3 cations:

CO₃^2-, NO^2-, S^2-, SO₃^2-, S₂O₃^2-, CH₃COO^-, F^-, Cl^-, Br^-, I^-, NO₃^-, BO₃^3-, C₂O₄^2-, PO₄^3-, NH₄⁺, K⁺,Pb²⁺, Cu²⁺, Cd²⁺, Bi³⁺, Sn²⁺, Sb³⁺, Fe³⁺, Al³⁺, Cr³⁺, Zn²⁺, Mn²⁺, Co²⁺, Ni²⁺, Ba²⁺,Sr²⁺, Ca²⁺,Mg²⁺.

Mixtures should preferably contain one interfering anion, or insoluble component (BaSO₄, SrSO₄, PbSO₄, CaF₂ or Al₂O₃) or combination of anions e.g. CO₃^2-and SO₃^2-, NO₂^- and NO₃^-, Cl^- and Br^-, Cl^- and I^-, Br- and I^-, NO₃^- and Br-, NO₃^- and I^-.

Spot tests should be done whenever possible.

Spectrophotometry

1. Measurement of 10 Dq by spectrophotometric method.
2. Verification of spectrochemical series.
3. Controlled synthesis of two copper oxalate hydrate complexes: kinetic vs thermodynamic factors.
4. Preparation of acetylacetanato complexes of Cu²⁺/Fe³⁺. Find the λ_max of the complex.
5. Synthesis of ammine complexes of Ni(II) and its ligand exchange reactions (e.g. bidentate ligands like acetylacetone, DMG, glycine) by substitution method.

Scheme of Examination

The duration of examination will be 5 hrs.

The following exercises will be set in the examination

Qualitative Mixture Analysis                                                        36 marks

Spectrophotometry                                                                    19 marks

Viva                                                                                          15 marks

Total                                                                                   70 marks

Qualitative Mixture Analysis

An inorganic mixture having 6 radicals carries 36 marks.  Mixture should contain either one interfering radical or one insoluble.

6 marks shall be awarded for each radical correctly reported. The distribution of marks will be as follows-

2 marks will be awarded for each correct radical if only dry test or preliminary tests are   given. 2 marks may be awarded to a candidate if she has approached in systematic and correct manner towards the analysis upto a group in analysis of basic radical or correct indicative test of acid radical. Remaining 2 mark is reserved for confirmatory test of radical.

Spectrophotometry

The exercise carries 19 marks. The distribution of marks will be as follows

Theory and procedure                                                               5 marks

Correct observation                                                                   5 marks

Use of correct formula and calculation                                        6 marks

Result                                                                                       3 marks

Viva

Oral questions shall generally be asked over the work assigned to the candidate. The purpose is to find out as to what extent the candidate has understood the basic principles.