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Friday, July 29, 2011
Essay on Walther Hermann Nernst, Josiah Willard Gibbs & Svante Arrhenius
Walther Hermann Nernst was a German Physicist who was well-known for his immense contribution in electrochemistry, thermodynamics, and photochemistry. Born in
in 1864, he became a pioneer in the field of chemical thermodynamics. One of his contributions is the third law of thermodynamics for which he was awarded the Nobel Prize in Chemistry in 1920. (Joachim Schummer 2) He spent his early years studying physical and mathematics in the Universities of Zurich, Berlin and Briesen, Prussia . He received his Ph.D. summa cum laude in 1887 for his doctoral thesis which was about the effects of magnetism and heat on electrical conductivity. In 1905, he was first appointed as professor of physical chemistry in Graz . In 1924, he became a professor of physics at Berlin . It was his close association with Wilhelm Ostwald and other physical chemists that Nernst began his important researches in the field of electrochemistry. Berlin
Nernst has always been interested with electrochemical studies. He was particularly interested with the dependence on concentration of galvanic cells such as batteries. He started by investigating the diffusion of electrolytes in one solution and compared the diffusion between two solutions with different electrolyte concentration.
One of the most important contributions of Nernst was made when he was in his twenties. He devised a mathematical expression showing that electromotive force is closely dependent upon temperature and concentration in a galvanic or electricity-producing cell. This was subsequently known as the Nernst Equation. The equation below shows what the Nernst Equation is:
Ecell = E0cell - (RT/nF)lnQ
The Nernst Equation may also be restated in the following manner
Ecell = E0cell - (2.303*RT/nF)logQ
at 298K, Ecell = E0cell - (0.0591 V/n)log Q
Based on the Nernst equation, the following are its values: Ecell = cell potential under nonstandard conditions (V); E0cell = cell potential under standard conditions; R = gas constant; T = temperature; n = number of moles of electrons exchanged in the electrochemical reaction; F = Faraday's constant; and Q = reaction quotient.
According to Walther Nernst, the Nernst equation is a useful equation as it allows the cell voltages to be predicted in a given reaction. It may also be used to find the concentration of one of the components of the cell. (Anne Marie Helmenstine 2) For instance, in case when a zinc electrode is submerged in a solution which is connected by a salt bridge to another solution containing a silver electrode. The Nernst equation can be helpful in determining the initial voltage of the cell given the particular solution. In this example, suppose that the first acidic solution is at 0.80 M Zn2+ solution while the second solution is at 1.30 M Ag+ solution. The cell potential can be determined which is at 1.57 V. (Anne Marie Helmenstein 2)
Josiah Willard Gibbs
Josiah Willard Gibbs was a famous American mathematical engineer who earned the distinction as one of the greatest mathematical physicist since Isaac Newton. He was also one of the few American physicists to gain recognition internationally for his contribution and achievement. (“Josiah Willard Gibbs2)
Born on February 11, 1830 in
, J. Willard Gibbs was known for devising the theoretical foundation for chemical thermodynamics as well as physical chemistry. He started his education at the local New Haven, Connecticut where he was described by his classmates as friendly but withdrawn which is an indication that he was involved very little in social life. Hopkins Grammar School Yale University and subsequently earned the Ph.D. in engineering in the same university in 1863 which was the first doctorate of engineering to be conferred in the . He initially taught Latin and natural philosophy until he left for United States New Haven to study in Europe where he attended lectures by scientists from Paris, Berlin and . He was later on appointed as professor of mathematical physics at Yale in 1871. Heidelberg
In simple terms, the Gibbs free energy states that energy that is unevenly distributed in a closed system will continue to move and be passed around until such time that there is no longer any further energy exchange possible. (“Science: Unknown Equilibrist” 2) This is what Gibbs called the thermodynamic equilibrium. How thermodynamic equilibrium is attained is explained using the Nernst Equation. The Gibbs Free Energy equation is one of the most important discovered of Josiah Willard Gibbs. Its equation is shown below:
G, is defined by G = H − TS,
In this equation, G is the energy that is being absorbed in a reversible process at constant pressure and constant temperature. H stands for the enthalpy while S stands for entropy. The changes in the values of G correspond to changes in free energy. It also presupposes that the process happens at a constant temperature and pressure.
Gibbs free energy is important because it determines when there will be a reaction depending on the changes in the values of G. It states the conditions when a chemical reaction will occur. For instance, when the ΔG is positive, it only means that the energy is in the equilibrium position. For this reason, there will be no chemical reaction unless energy is supplied or added so that the equilibrium will be changed. On the other hand, when the ΔG is negative there is a spontaneous chemical reaction which will proceed to equilibrium.
Svante Arrhenius is considered as one of the founders of physical chemistry or the field of science in which physical laws are used to explain chemical phenomena. He was born on February 19, 1859 in
. His intelligence became manifest at a young age of three where he taught himself how to read which was surprisingly against the wishes of his parents. He also acquired an excellent mathematical skill just by observing his father perform accounting work. His interests as a young boy were mathematics and physics. He entered the Sweden studying mathematics, chemistry and physics. He eventually left University of Uppsala Uppsala in 1881 to work on the conductivities of electrolytes at under the famous physicist E. Edlund. His association with Edlund led to the preparation of a thesis entitled Investigations on the galvanic conductivity of electrolytes where he concluded that electrolytes when dissolved in water become split or dissociated into electrically opposite and negative ions. He also concluded that the degree of dissociation depended on many factors such as the nature of the substance and the concentration of its solution. (“Svante Arrhenius: Biography” 2004) Surprisingly, his ideas were not accepted by the faculty. As a result, he barely passed his dissertation. Stockholm
The Arrhenius Equation is shown below:
In this equation, T refers to the temperature which is measured in Kelvin. R refers to the gas constant which is measured in R. EA refers to the activation energy. The Arrhenius Equation simply states that when the temperature remains constant, chemical reaction will not be any faster or slower. However, when the temperature becomes higher, chemical reaction will also happen faster. This is because the molecule particles start to collide at a faster rate. As the molecules react to the change in temperature and as they move faster, the greater will be the number of collisions that can lead to a reaction. In simple words, the higher the collision rate the higher the resulting kinetic energy which leads to a chemical reaction.
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