Physical Chemistry - CR

Objectives

This subject aims at conferring the students the principles of Physical Chemistry necessary to raise adequate questions to an interpretation of situations to be found in the field of Conservation & Restoration.[1]

Specific objectives are the following: i) quantify chemical equilibrium and fully characterize it in thermodynamic grounds; ii) quantify ion transport in solution; iii) characterize the kinetics of a chemical reaction; iv) understand the principles behind current spectroscopic methods, in particular IR and UV-vis spectroscopies.

In laboratory, the following skills are expected to be developed/acquired: i) design experiments to test a given hypothesis; ii) plan experiments to characterize the kinetics of a chemical reaction or of an ageing process; iii) use UV-vis spectroscopy to characterize compounds and follow reactions.

 

[1] Physical Chemistry is a key subject to other subjects that appear later on in LCR as well as in CR Master courses, e. g., Polymers in Conservation, Diagnostic subjects, Analytical Methods I e II, History and Techniques of Artistic Production).

 

General characterization

Code

10873

Credits

9.0

Responsible teacher

António Jorge Dias Parola

Hours

Weekly - 5

Total - 80

Teaching language

Português

Prerequisites

This subject requires students to be acquainted with basic knowledge in solution chemistry (for thermodynamics and kinetics) and in the structure of matter (for spectroscopy), provided by previous chemistry related subjects of LCR (Principles of Chemistry and Laboratory Security Good Practices (1st semester), Inorganic Chemistry (CR) (2nd semester) and Organic Chemistry (CR) (3rd semester)).

 

Bibliography

P. Atkins, J. de Paula, Elements of Physical Chemistry, 6thEd., Oxford University Press, 2013.

P. Atkins, J. de Paula, Atkins’ Physical Chemistry, 9thEd., Oxford University Press, 2010.

Teaching method

The teaching of Physical-Chemistry is in portuguese, spread over 39 h of theoretical lessons, complemented by 9 h of exercises and problem solving. The experimental part includes 21 h of laboratory practice, where the students prepare an experiment and carry it out.

Students have access to a webpage in CLIP where the experimental protocols, syllabus, exercises, problems, and old exams as well as several data tables are available. 

Evaluation method

This curricular unit (CU) has attendance (“frequência”). To comply with this, it is necessary to perform all the laboratory classes, submit the respective questionnaires or reports, and have a practical grade ≥ 9.5. Students who have attendance from previous years do not need to take practical classes; the grade previously obtained will be used in the calculation of the final grade.

The final grade of this CU has a contribution of 60% of the theoretical grade and 40% of the practical grade.

The evaluation of the theoretical component is based on the completion of three tests or an exam. Completing the CU by tests means taking the 3 tests and having an average of ≥ 9.5 values. This average, or the exam grade, has a weight of 60% in the final grade.

In the experimental part, the students must deliver answers to simple questionnaires relating to three of the laboratoty lessons and three reports, two relating to the remaining practical works and the third relating to the mini-project. The reports and questionnaires are subject to oral discussion (one of them in the middle of the semester so that the students do not repeat errors in the two subsequent reports). The mini-project requires an oral presentation of 15 minutes (followed by 5 to 10 minutes of discussion) in a public session that takes place in the last week of the semester.

The evaluation of the practical component has three contributions: i) evaluation of the preparation of the laboratory experiment and personal performance during the classroom, ii) evaluation of the two questionnaires and two reports of the practical work and the mini-laboratory project after oral discussion, iii) public oral presentation of the mini-project, followed by a short discussion. This is translated into a practical grade (NP) given by: NP=0.4xNR+0.25xNQ+0.35x(NP+OP)/2, where NR is the average of the grades of the two reports, NQ is the average of the grades of the three questionnaires, NP is the grade of the mini-project report and OP is the grade of the oral presentation and discussion of the mini-project. The practical grade must be ≥ 9.5.

 

In carrying out any evaluation procedure, it must be take into consideration the provisions of Article 10 of the FCT NOVA Evaluation Regulation, “When the existence of fraud or plagiarism is verified, in any of the two evaluation elements of a CU, the students directly involved are preliminarily disqualified from UC (…).”

Subject matter

1. Revision of concepts acquired in the subject Principles of Chemistry

1.1 Chemical reactions

Spontaneous chemical reactions. Gibbs function. Exoergonic and endoergonic reactions. Chemical equilibrium and its response to changes in experimental conditions. Applications of the concept of chemical equilibrium.

1.2 Electrochemical equilibrium

Thermodynamic properties of ions in solution. Ionic strength. Debye-Hückel law. Electrochemical cells. Nernst equation. Applications: the electrochemical series; solubility constants; measurement of pH, pKa, pX; thermodynamic functions from cell potential measurements; potentiometric titrations.

2. Ion transport and molecular diffusion

Conductivity. Strong and weak electrolytes. Degree of ionization. Kohlrausch’s law and Ostwald’s dilution law. Diffusion. Reference to Fick’s law.

3. Chemical kinetics

Experimental techniques. The rates of reactions. The rate law: rate constant, reaction order. Differential method and integrated rate laws. Half-lives. Reactions approaching equilibrium. Relaxation methods. Dependence of reaction rate on temperature.

Accounting for the rate laws. Consecutive elementary reactions. The rate-determining step. The steady-state approximation. The Michaelis-Menten mechanism. Unimolecular reactions.

4. Molecular spectroscopy

Some important results from quantum mechanics. Electromagnetic radiation and its interaction with atoms and molecules. Molecular symmetry and group theory. Vibrational spectroscopy. Electronic spectroscopy.

5. Basic processes in Molecular Photochemistry

Quantum yields. Excited state lifetime. Bimolecular processes, Ster-Volmer kinetics.

 

In the laboratory:

There is a pool of 8 experimental procedures, 5 of which are each year selected:

T1: Acid-base titration of an anthocyanin followed by UV-vis spectrophotometry. Reds, violets and blues in nature.

T2: Ionic conductivity of weak and strong electrolytes.

T3: Measurement of contact angles in solid-liquid interfaces.

T4: Kinetics of the thermal reduction of toluidine blue with sulfite

T5: Kinetics of the degradation of benomyl in organic solvents

T6: Quantum yield of the photochemical aquation of potassium hexacyanocobaltate(III).

T7: UV-vis spectra of cyanins.

 

There are two laboratory lessons where each group of three students carries out procedures related to a specific problem in Conservation and Restoration.

 

Programs

Programs where the course is taught: