Chemical Weathering
Chemical weathering occurs when rainwater reacts with the grains of minerals in rocks to form soluble salts and clays. In particular, these reactions occur when the water is slightly acidic (Little and Lee 31). Chemical weathering especially oxidation, dissolution, and hydrolysis is the first step in the production of soils.
Hydrolysis
By definition, hydrolysis refers to a reaction that involves the bond breaking in a molecule by the use of water. The kind of reaction mainly occurs between the molecules of water and anion, and often, it results in the change of the pH of a solution. Normally, there are a total of three main types of hydrolysis in chemistry. In particular, they include acid, salt, and base hydrolysis. Hydrolysis can be said to be the reverse of the reaction of condensation in which two molecules are joined together into a larger one. In the process, water is added to break down (White 69). At the same time, condensation builds up by the removal of any other solvents including water.
Salt Hydrolysis
In salt hydrolysis, water spontaneously ionizes into both hydronium cations and hydroxide anions. Additionally, the salt dissociates into its constituent cations and anions. For instance, sodium acetate can dissociate in water into acetate and sodium ions (Ohta and Arai 280). As a result, there is a production of a relatively basic solution, an excess of hydroxide ions. Moreover, it is possible for strong acid also to undergo hydrolysis (Little and Lee 33). In this case, H2SO4 (sulfuric acid) can be dissolved in water to produce bisulfate and hydronium, the conjugate base of the sulfuric acid. Remember, salts dissociate to form ions either incompletely or entirely depending on the respective constant of solubility (White 72). For example,
In this reaction, putting NH4Br in water make it dissociate into Br and NH4
Acid Hydrolysis
In acid hydrolysis, water can either accept or donate H+ (a proton). In this reaction, water donates the proton from the acetic acid (CH3COOH) to form a hydronium ion or conjugate base (White 77). Also, there is a production of a hydronium when a weak acid is hydrolyzed.
In the real world, a living organism can only live by processing fuel for making energy. Such energy that is converted from fuel is alter stored in the Adenosine Triphosphate (ATP) molecules. In life, many processes are required for sustainability (Ohta and Arai 284). These processes include muscle contraction, neurotransmitters in the brain, respiration, hormones distribution and so on. An input of energy is required in all these important processes.
Dissolution
In chemical weathering, dissolution involves causing a solid material to pass through a solution. Typically, the process consists in making a solid to go through a liquid phase (White 86). For example, the formation of alloys makes a solid dissolve into another for the creation of a solution. For a process to be considered a dissolution, some specific criteria have to be met. For gases and liquids, the substance that dissolves must have the capacity to form interactions that are non-covalent with the solvent (Little and Lee 39). The structure of the crystal needs to be broken up for releasing either molecules, ions, or atoms for crystalline solids.
In dissolution, the original rock is fully dissolved by acid, leaving no solid behind. For example, the carbonic acid's progressive action on limestone over a very long span of time is responsible for all of the spectacular limestone caves in the world (Ohta and Arai 283). The separation of solids makes its anions and cations dissolve. The soluble ionic compounds' dissociation gives solutions of such compounds a unique property that allows them to conduct electricity.
Oxidation
Oxidation is the process of breaking down rock by water and oxygen. In most cases, the iron-rich rock is given a rusty-colored weathered surface. It is also said to be any reaction of chemicals that involves the movement of electrons. In simple terms, there is oxidation of a substance that gives away electrons. A chemical called rust is formed when oxygen reacts with iron. During the reaction, the oxygen gains some electrons that are lost by the iron. A reduction is the exact opposite of oxidation (Ohta and Arai 293). For this reason, an oxidation-reaction always comes together with a reduction-reaction. Reduction and oxidation together are known as redox. In a reaction, it is not a must for oxygen to be present for it to be a redox. Remember, rusting is one of the classic examples of the redox reaction.
At its basic level, oxidation is the gain of oxygen and the loss of electrons. Both the oxidation and reduction go on at the same time which is called a redox reaction. Oxidation may start artificially or be a spontaneous process. It can either be destructive or helpful. A property of a compound or atom changes when it is oxidized (Little and Lee 43). Unoxidized iron is said to be structurally sound and strong metal, while the oxidized one is reddish powder and brittle. An oxidized iron carries charge. Because of its ease of oxidation, it is important to reduce its exposure to moisture and oxygen (Ohta and Arai 297). In most cases, oxidation takes place in tandem with the process of reduction.
Works Cited
Little, M.G., and C.-T.A. Lee. "Chemical Weathering and Transport of Heat in Active Mountain Belts by Groundwater: Evidence from Coupled Models of Mechanical and Chemical Weathering, Inverted Weathering Profiles, And Low Heat Flow." Geochimica Et Cosmochimica Acta, vol. 70, no. 18, 2006, pp. 31-43. Elsevier BV, doi: 10.1016/j.gca.2006.06.734.
Ohta, Tohru, and Hiroyoshi Arai. "Statistical Empirical Index of Chemical Weathering in Igneous Rocks: A New Tool for Evaluating the Degree of Weathering." Chemical Geology, vol. 240, no. 3-4, 2007, pp. 280-297. Elsevier BV, doi: 10.1016/j.chemgeo.2007.02.017.
White, Art F. "Determining Mineral Weathering Rates Based on Solid and Solute Weathering Gradients and Velocities: Application to Biotite Weathering in Saprolites." Chemical Geology, vol. 190, no. 1-4, 2002, pp. 69-89. Elsevier BV, doi:10.1016/s0009-2541(02)00111-0.
