## Spectroscopy and kinetics (CH2101)

### Aims

The module aims to provide the student with an understanding of how properties and events at the atomic level lead to changes and processes that can be measured at a macroscopic level. Two major themes are developed; the properties of gases leading to the derivation of the laws describing the rates of chemical change and the interaction of electromagnetic radiation with matter and its application in spectroscopic techniques.

### General description

Gas kinetics will be used to derive the ideal gas laws and extended to reactions using simple collision theory. Transition state theory of kinetics will also be developed and the order of reaction and rate equations introduced. The equilibrium structures of molecules will be discussed with reference to experimental determination of structure via X-ray diffraction. Energy changes in spectroscopy will be discussed with reference to atomic spectroscopy and its use to derive the orbital model of the atomic state from the line spectrum of the hydrogen atom and the Rydberg formula. Much of the material will be taught through IT practicals as part of the laboratory programme associated with the course.

### Syllabus content

#### Gas and reaction kinetics:

The kinetic model of gases: Empirical gas laws and the Ideal Gas Equation; the pressure of a gas according to the kinetic model and the derivation of the Ideal Gas Equation. Real gases, the van der Waals equation of state; the Maxwell distribution of speeds; Graham’s law of effusion; molecular collision frequencies. The formulation of rate equations from collision theory; molecularity and order of reactions the integrated rate laws (zero, 1st and 2nd order); the effect of temperature on reaction, the Arrhenius equation. Improved theories of reaction rates. The steric factor; activated complex theory. Experimental methods for studying rates.

#### Spectroscopy:

Electromagnetic spectrum and the principles of spectroscopy. Molecular energy storage - electronic vibrational, rotational and translational excitation. Absorption and emission processes, Beer-Lambert law. H atom line spectrum and Rydberg formula. Diffraction of light and of electrons. Wave-particle duality.

#### Practical work:

Experience of UV-visible and IR spectroscopies; hydrogen line spectrum. Diffraction of X-rays and electrons by solids. Practice in determining molecular and atomic information from raw data. Measurement of kinetic parameters experimentally and in IT simulations.