Chem 113- week 3
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This 2 page Class Notes was uploaded by Alexis Darling on Friday February 5, 2016. The Class Notes belongs to CHEM 113 at Colorado State University taught by Ingrid Marie Laughman in Fall 2015. Since its upload, it has received 8 views.
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Date Created: 02/05/16
Week 3 12.7 Considering the equation ΔG=ΔHTΔS, as T increases, ΔG goes down because T is subtracted, and ΔS and ΔH can be considered constant. So at lower temperatures, ΔG is a larger positive number, but at higher temperatures past equilibrium ΔG is a more negative number. This means that reactions can be nonspontaneous at lower temperatures and spontaneous at higher temperatures. When ΔG=0, the system is at equilibrium and the same number of reactants that turn to products is the same as the number of products turning to reactants in that time (no net change). 12.8 Living systems couple spontaneous and nonspontaneous reactions so that they utilize them together to continue growth. Spontaneous reactions are needed for energy which pushes nonspontaneous reactions to occur so that the organisms can build. One example is glycolysis, which includes a phosphorylation step. This nonspontaneous reaction is fueled by ATP. 13.1 Photochemical smog results from the nitrogen monoxide released from vehicles reacting with oxygen in the air to produce nitrogen dioxide, only to break apart in the sunlight back into NO and oxygen atoms which form ozone with existing O in th2 air or hydroxyl radicals with existing water vapor. Chemical kinetics allows us to know the rates of change between certain reactants and products so that we can create devices to minimize them. 13.2 As reactants become products in a regular reaction, they have a negative rate of change because their amount decreases, but the reaction rate is positive because this rate tells how fast a reaction (going from reactants to products) occurs. Therefore a decrease in reactants means an increase in products and positive reaction rate. Reaction rates are expressed in concentration/molarity, meaning moles divided by liters, over time. Each rate of change is influenced by a factor of the reciprocal of the coefficient of that reactant or product in the balanced chemical equation. The rates of change are determined by recording the results of experiments. Always choose the rate of change of the reactant or product with a coefficient of 1 in the equation to be representative of the overall reaction. The instantaneous rate of reaction is different as a reaction proceeds: it begins with a high rate, then slows until it reaches equilibrium. Instantaneous rates can be found on a graph of concentration versus time by drawing a tangent at the desired moment. 13.5 A reaction mechanism includes a different number of elementary steps which involve intermediates, or molecules changed from the initial reactants but before they move on towards creating the final molecules/products. They can exist for just a moment or a long enough time that they have been isolated. Activated complexes only exist for a moment. The molecularity of an elementary step can involve one (uni), two (bi), or rarely three (ter) molecules colliding. The sums of elementary steps result in the stoichiometric equation. Each elementary step has its own energy of activation. Whichever step is the slowest is known as the rate determining step.
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