Course program
Analytical problems and their solutions
Description of the role of analytical chemistry and its applications in science. Description of the steps in a general analytical workflow: method choice, sampling, sample preparation and other operations before analysis (sample solubilisation, analyte separation), sample analysis by classical and instrumental assays, data analysis. Thermodynamic and kinetic considerations on in solution chemical equilibria. (2h).
Redox reactions and acidity
Outlines on homogeneous equilibria (acid-base, redox equilibria). Nernst equation. Factors affecting the kinetics of a chemical reaction. Effect of pH on redox reactions. Selective recognition of halides (chlorides, bromides and iodides) by permanganate. The redox couple nitrite/nitric oxide. Disproportionation and pH (study case of halogens and hydrogen peroxide). (4h)
Complexes, acidity and redox reactions
Definition of complexes. Factors affecting the stability of a complex (dilution, solvent medium, ionic strength). Effect of pH on complexes constituted by ligands which are conjugate bases of weak acids. Variations of the redox potential due to complex formation. Influence of the instability constant on the redox potential. Effect of complexation on the potential of a redox couple. Stabilization of an unstable redox state by complexation (case study, Mn (III)) (3h).
Precipitation equilibria, solubility and pH
Heterogeneous equilibria. Definition of solubility product, relation between Kps and solubility. Factors which affect the solubility of slightly soluble compounds (ionic strength, activity, solvent medium, dilution, pH, common ion effect). Solubility of a slightly soluble compound deriving from weak monoprotic acid. Chemistry of sulfates, carbonates, oxalate. Calculation of the precipitation pH of a sulfate. Sulfates dissolution. Sulfates dissolution by formation of salts and thiosalts, acid-base and redox reactions. Sulfate solubility and pH. Hydroxide chemistry and the case study of aluminium hydroxide (amphoteric oxide) and of zinc hydroxide. Hydroxide amphoterism and related causes. Solubility of amphoteric hydroxides as a function of pH. Precipitate formation. Colloidal precipitates. Adsorption, aging of precipitates, postprecipitation (10 h).
Solubility and complexation
Precipitation of an insoluble compound from a complex. Reactions of thiocompounds. Dissolution of a precipitate by complexation (1h).
Precipitation and redox reactions
Oxidation and precipitation. The case study of Fe2+/Fe3+. Variation of the redox properties by salt precipitation. Stabilization of an oxidation state by precipitation (case study of mercury chemistry). Complexes and redox reactions. Disproportionation induced by precipitation (2h).
Classification of separation methods
Liquid-liquid extraction. Phase distribution and Nernst equation. Definition of distribution constant and distribution ratio. Theoretical principles on extraction. Extraction efficiency and selectivity. Factors which affect extraction equilibria. Extractability of acids and bases. Separation techniques and related physico-chemical principles. Extractability of cations, pH dependence. Logarithmic curves (2h).
Laboratory activity (with description of the practical activities)
The laboratory actives are usually held in groups of 50 students and are organized according to the following experiences:
1-assignment of the position and the required labware and glassware. Description of how to employ a centrifuge (time required ~ 1.5 h)
2-Experience 1: solubility in strong acids (nitric acid, hydrochloric acid, sulphuric acid). (time required ~ 3 h)
3-Experience 2: solubility in bases (sodium hydroxide and ammonia) (time required ~ 3 h)
4-Experience 3: oxidation and pH (selective oxidation of halides by permanganate) (time required ~ 4 h)
5-Experience 4: solubility equilibria as a function of pH and complexation. Reactivity test and recognition of Al3+, Fe2+, Fe3+ e Cr3+ (time required ~ 3 h)
6-Experience 5: solubility equilibria as a function of pH and complexation (time required ~ 3 h)
6- Experience 6: separation of Ag+, Zn2+ and Mn+2 by precipitation at controlled pH (time required ~ 4 h)
7-Experience 7: separation of Cu2+, Hg2+, As3+, Ni2+ and Co+2 by precipitation at controlled pH (time required ~ 4 h)
8-Unknown ion assay (time required ~ 4 h)
9- Unknown ion assay 2 (time required ~ 4 h)
10-Restitution of labware and glassware (time required ~ 1 h)
Prerequisites
From the previous courses the student should already have acquired basic knowledge of the chemical language and the basic knowledge about acid-base equilibria, pH, oxidation number definition and calculation, redox reactions and their balancing. For the aim of the course, it is also useful to have previous knowledge about the distinction between electrolytes and non-electrolytes, strong and weak electrolytes, and basic knowledge on the description of chemical equilibria by means of equilibria constants and Le Chatelier principle.
Books
-Araneo A. “Chimica Analitica Qualitativa: Nuovo Metodo Periodale”, Casa Editrice Ambrosiana Milano
-Douglas A.Skoog, Donald M. West, F. James Holler. “Fondamenti di Chimica Analitica”, EdiSES S.r.l. Napoli
Teaching mode
The course is held by a traditional didactic teaching method, which does not only provide the basic knowledge of analytical chemistry, but it also provides the means by which the theoretical knowledge can be applied to the study of reactions, at both a practical and theoretical level. These latest aims are reached by explanation of selected exercises, study cases and by the laboratory experiences, which include the writing of a report.
Frequency
Lesson attendance is not mandatory for the exam, but laboratory experiences are
Exam mode
In order to take the exam, the student must book a proper date on the INFOSTUD site:
https://stud.infostud.uniroma1.it/Sest/Log/
The period in which exams take place is decided at the beginning of every academic year. Exam sessions begin at the end of the teaching activity of each course.
The exam is made up two parts, i.e. a practical experiment at the end of the didactic laboratory and an oral exam. To pass the exam, the final mark must not be less than 18/30. Passing the exam provides 9 CFU.
During the exam, the capacity of the student to solve problems of analytical chemistry will be evaluated, such as the separation of different inorganic analytes in a complex mixture, so to selectively isolate them by applying the knowledge provided in the course. The attendance to the didactic laboratory is considered for evaluation, and more importantly the reasoning capacity in the solution of an analytical problem (logic of the proposed solution, correctness of the solution compared to the knowledge the student is supposed to possess at the end of the course, language correctness). More specifically, in the choice of the final mark the following features are considered:
1. reasoning capacity;
2. clarity and completeness in the oral presentation of the contents of the course;
3. mastery in the writing and balancing of chemical equations and in the solving of analytical chemistry problems;
4. critical evaluation capacity of exercise results and of the experimental procedures;
5. capacity of linking contents from different topics.
Lesson mode
The course is held by a traditional didactic teaching method, which does not only provide the basic knowledge of analytical chemistry, but it also provides the means by which the theoretical knowledge can be applied to the study of reactions, at both a practical and theoretical level. These latest aims are reached by explanation of selected exercises, study cases and by the laboratory experiences, which include the writing of a report.