Chemistry answers and questions

  What are free energy functions? Significance of Gibbs free energy and Helmholtz free energy. Free Energy Functions: In natural processes there are two factors involved when a system approaches equilibrium. One is the tendency to minimum energy and other is the tendency to maximum entropy. In many cases these two tendencies are in competition. If entropy or energy changes were only involved in deciding the direction of change, some strange phenomena would be observed. For example, if the approach to equilibrium were governed solely by the criterion of lowest energy, all liquids would simultaneously freeze at any temperature, since energy is liberated on freezing. On the other hand, criterion of approach to equilibrium as the state of maximum disorder or entropy would result in all solids spontaneously melting or even evaporating since both processes involve an increase in disorder. In practice, two tendencies often reached a compromise, which usually depends on temperatu...

  What is 3c-2e Bond? How 3c-2e bond can be explained with the help of diboranes? Three center two electron bond: 3c-2e bond is formed by elements which can form electron deficient compounds. Here two electrons are shared by three nuclei.   Three atomic orbitals from three molecular orbitals combine to form one bonding, one non- bonding and one anti-bonding molecular orbital. The electrons go into bonding molecular orbital resulting in a net bonding effect and a chemical bond is formed among three atoms. In these bonds the bonding orbital is shifted toward two of three atoms instead of being spread equally among three. An example of this type of bond is trihydrogen cation  H 3 + . It is also called banana or bent bond. Bonding in Boranes: An extended version of the 3c–2e bond model features heavily in  cluster compounds  described by the polyhedral skeletal electron pair theory, such as  boranes  and  carboranes . These molecules deriv...

  What is Spectrochemical Series? Which Factors influence the order of ligands in Spectrochemical series? Spectrochemical series: In coordination chemistry, ligands do not influence the metal ions equally. Some ligands produce small crystal field stabilizing energy (∆) are called weak field ligands. Ligands that produce large crystal field stabilizing energy (∆) are called strong field ligands. A series has been developed called spectrochemical series. This series is fundamental because it connects ligand strength, crystal field splitting and spin state making it one of the most powerful tools for predicting the properties of coordination compounds. Definition: Spectrochemical series is arrangement of ligands in order of their ability to increase crystal field stabilization. It is based on spectroscopic data, experimental observation and magnetic properties of complexes.     Ligands on left side produce small splitting while on the right side produce lar...

  What is Jahn Teller Theorem? How various spin states exhibit Jahn Teller distortions? Spectroscopy and Jahn Teller distortions.   Jahn teller theorem: In 1937, Herman Jahn and Edward Teller postulated a theorem stating that” stability and degeneracy are not possible simultaneously unless the molecule is a linear one.” This leads to a break in degeneracy which stabilizes the molecule and as a result its symmetry is reduced. Housecroft and Sharpe have eloquently phrased it as " any non-linear molecular system in a degenerate electronic state will be unstable and will undergo distortion to form a system of lower symmetry and lower energy thereby removing the degeneracy" Jahn Teller theorem is also known as Jahn Teller Distortions. Jahn Teller Distortions in Octahedral complexes: Although this is commonly observed with octahedral complexes, tetrahedral complexes also can undergo these Jahn Teller distortions. In an octahedral complex five d atomic orbitals are...