LABORATORY FOR PHYSICAL CHEMISTRY I
Learning outcomes of the course unit
By carrying out exercises and experiments, the student will deepen and consolidate his knowledge of Chemical Thermodynamics, Chemical Kinetics and Electrochemistry, especially for what concerns the practical aspects, the acquisition and the critical analysis of the experimental data and the information that these data provide.
The classroom and laboratory activities will give the student the opportunity of closely interacting with the teacher and with the other students, encouraging him to express free opinions and personal considerations in order to develop communication skill and critical sense.
The topics dealt with in the Physical Chemistry 1 are fundamental for the understanding and correctly interpreting the chemical transformations. In this context, the practice has the aim of strengthening the abilities of the student to deal with subjects like the reactivity, the reaction mechanisms, the chemical equilibria, and so on, which are central and recurring along the whole formation pathway of a graduate in Chemistry.
Course contents summary
The course constitutes an adequate support and integration of the Physical Chemistry 1 course. The subjects developed in this ambit will be applied to the resolution of problems and to the laboratory practice.
1. Introductory lessons.
Safety and behavior rules in laboratory.
The error theory. The measurement of physical quantities. Types of measurement. Types of error: precision and accuracy. Mean value. The evaluation of the uncertainty. How to express the experimental data. Propagation of the experimental errors. The method of least squares. Linear regression.
2. Integrative lessons.
Experimental thermochemistry. Principles of calorimetry. The adiabatic calorimetric bomb. Differential Scanning Calorimetry (DSC). The Regnault calorimeter.
Conductivity of electrolytic solutions. Conductivity: definition and units. Ionic or electrolytic conductors. Specific conductivity. Molar and equivalent conductivity. Equivalent conductivity at infinite dilution. Onsager equation. Law of independent ion migration. Limiting equivalent ionic conductivity. Ionic mobility. Weak electrolytes: the dissociation degree. The Ostwald dilution law. The conductometer: working principles.
Electrochemistry. Types of electrodes. Semi-reactions. Liquid junction potential. Cell reactions. Cell potential and electric work. Absolute difference of potential. Relationship between electrical and thermodynamic quantities. The Nernst equation. The concentration cell. The electrochemical equilibrium. Standard potentials and their measurement. The equilibrium constant calculation. The measurement of the activity coefficients. The electrochemical series. The temperature coefficient of the absolute difference of potential and the calculation of the thermodynamic quantities.
Chemical kinetics. Reaction rate: definition. Kinetic laws, order reaction and kinetic constant. Integrated kinetic laws. The half-life. The Arrhenius law and the activation energy. Experimental techniques in chemical kinetics: the monitoring of the evolution of a chemical reaction. Methodologies: real time analysis, extinction methods, flux techniques, flash photolysis. Analysis of the kinetic measurements: the integration method, the initial rate method, the half-life method, the insulation method.
3. Numerical exercises
The laws of gases. Ideal gas, van der Waals gas. Reduced variables. Principle of the corresponding states.
Thermodynamics of the ideal gas. Thermal capacity. Reversible and irreversible isothermal transformation. Reversible and irreversible adiabatic transformation.
Thermochemistry. Reaction enthalpy and energy. The Kirchoff law. The Hess law.
Second principle of thermodynamics. Entropy variations of the system, of the ambient, of the universe. Spontaneity of a process. Gibbs and Helmholtz energies, working function. S and G in: heating or cooling processes, isothermal expansion or compression, chemical reactions, phase transitions.
Chemical equilibrium. Reaction quotient and equilibrium constant. van’t Hoff law.
Mixtures and solutions. Vapor pressure and Raoult law. Ideal solutions. Partial molar quantities. Colligative properties: osmotic pressure, boiling point elevation and freezing point depression. Mixing entropy and Gibbs energy.
Phase equilibria. Clapeyron and Clausius-Clapeyron equations.
Electrochemistry. Cell potentials. Standard potentials. Electrochemical cells. Electrode reactions. Semi-reactions. Absolute difference of potential and Gibbs energy. Nernst equation. Temperature coefficient of the absolute difference of potential and thermodynamic properties. Activity and mean ionic activity coefficients. Debye–Hückel limiting law and its modifications. Ionic strength.
Chemical kinetics. Reaction rate. Kinetic laws and order reaction. Integrated kinetic laws. Kinetic constant and Arrhenius law.
4. Laboratory experiments.
i. Pressure vapor measurements and determination of the vaporization heat of a pure liquid (acetone).
ii. Determination of the pKa of an indicator by spectrophotometric measurements.
iii. Determination of formation heat of some ions by calorimetric measurements.
iv. Determination of the solubility of an scarcely soluble salt by conductometric measurements.
v. Conductivity of electrolytes in solution.
vi. Determination of the standard potential of the Zn2+/Zn electrode.
vii. Thermodynamics of the cell reaction in a commercial battery.
viii. Study of the kinetics of the hydrolysis of 2-chloro-2-metilbuthane through conductometric measurements.
ix. Study of the kinetics of the reaction between violet crystal and NaOH through spectrophotometric measurements.
Sillen: Problemi di Chimica Fisica - Piccin Editore Padova
P.W.Atkins: Chimica Fisica - Zanichelli Bologna
A.M.Halpern: Experimental Physical Chemistry - 1997 -Prentice Hall
Lionel M.Raff: Principles of Physical Chemistry - 2001 - Prentice Hall
W.J.Moore : Chimica Fisica - Piccin Editore Padova
Assessment methods and criteria
The preparation of the students will be verified through the evaluation of the laboratory reports and completed by a written test. The final evaluation will be given in the ambit of the final exam (Physical Chemistry 1 and Laboratory of Physical Chemistry 1), that could include a discussion concerning the work carried out.