EXPERIMENT NO. 9 CHEMICAL EQUILIBRIUM Audrey De Castro FCD3, Group 9, Ms. Sarah Sibug Kristine Tavares March 27, 2014 I. ABSTRACT
Chemical equilibrium is mostly involved in industrial processes such as synthesis of ammonia gas, formation of sulfuric acid and methanol. It is also behind some of the natural phenomena like lime production from limestone. (Application of Chemical, n.d.) In experiment 9, the response of a system in chemical equilibrium to disturbances or changes was observed. The objectives of the experiment was to evaluate how changes in concentration and temperature affect the equilibrium system, explain and interpret the results based on Le Chatelier’s principle. The shifts in the position of the equilibrium were induced by the change in concentration and temperature. In changing the concentration, different reagents were added to a solution at equilibrium state. In changing the temperature, a solution inside a test tube was heated while another one was cooled. The changes in color of the solution indicated that a shift in the equilibrium occurred. II. KEYWORDS: Chemical equilibrium, Le Chatelier’s Principle, dissociation, common ion effect, uncommon ion effect, shift III. INTRODUCTION
Chemical equilibrium is reached when opposing reactions- forward and reverse reactions- occur at the same rate. This means that the rate at which the reaction forms the products is equal to the rate at which the reaction forms the reactants (Lemay et al, 2012). In this dynamic state, there is continuous formation of reactant and products (Committee on General Chemistry, 2012, p. 76). This principle is used to explain some natural phenomena. Furthermore, it is often used in industrial chemical processes such as synthesis of ammonia and production of limestone (Brown, 2013).
At the state of chemical equilibrium, concentrations of both the reactants and the products no longer change; making it seem like the reaction has stopped. (Lemay et al, 2013) However, a reaction in equilibrium could be disturbed by changes in concentration, temperature and pressure. The effects of the change in concentration and temperature were observed in the experiment.
According to Le Chatelier’s principle, if a change that disturbs a system in equilibrium is done, the position of the equilibrium moves in order to counteract the change (Clark, 2002). This principle served as the basis for the explanation for the results observed in the experiment (Committee on General Chemistry, 2012, p. 76).
In the first part of the experiment, a solution was prepared by placing 20 drops of 1 M Ferric nitrate (Fe (NO3)3 ), 20 drops of 1 M Potassium thiocyanate (KCNS) and 7 ml of water in a 10 mL test tube. After shaking the solution well, the color of the mixture was recorded. Next, 8 test tubes were labelled from 1 to 8. Each had 10 drops of the solution prepared.
In the first six test tubes, 10 drops each of the following reagents: distilled water, 0.1 M Fe(NO3)3 , 0.1 M KCNS, 0.1 M KCl, 0.1 M AgCH3OO and a pinch of NaF , were added respectively. Using test tube #1 as reference, the changes in intensity of color or appearance of the mixture was observed and taken note of. The first six test tubes indicated the effects of changes in concentration to the equilibrium system.
Meanwhile, 10 drops of distilled water were both added to test tubes 7 and 8. Test tube # 7 was heated using an alcohol lamp while test tube 8 was placed in an ice water bath, a set-up wherein you just put the ice water in a beaker then put the test tube in that beaker. The last two test tubes showed the...
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