Experiment1 - problems sets for ns102 course

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40 EXPERIMENT 1 UNDERSTANDING EQUILIBRIUM PURPOSE: To understand the dynamic equilibrium in chemical reactions and to examine the effects of concentration and temperature on equilibrium. To understand the energy changes taking place during a chemical reaction. APPARATUS AND CHEMICALS 0.2M Copper sulfate Concentrated hydrochloric acid (HCl) Sodium chloride (NaCl) Urea 50 ml Beaker Calcium chloride Ice bath Barium hydroxide Glass rod Ammonium chloride THEORETICAL BACKGROUND A. Reactions at equilibrium When you write a chemical equation involving the reactants A and B forming the products C and D, you are really describing two reactions; the forward reaction , which converts reactants into products , A + B C + D and the corresponding back reaction , which converts products into reactants C + D A + B . The back reaction prevents the reactants from completely converting to products, and in time, the forward and back reactions strike a balance and the reaction appears to stop. In reality, the forward and reverse reactions are still going. What does stop changing is the ratio of the amount of products to reactants because, at this point, for any reactants that complete the forward reaction some products complete the back reaction to keep the balance. This condition, where molecules are switching equally between products and reactants while maintaining a constant overall ratio, is called equilibrium .
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41 The reactions in equilibrium are dynamic and respond to stress or perturbations in a logical way. For instance, add more reactants to a reaction at equilibrium, and the reaction shifts to make more products and return to a balanced equilibrium. Remove some reactants and the reaction shifts into reverse to replace them. Heat can be a reactant or product too. A reaction that produces heat as a product shifts back to making reactants if you add more heat (by
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Experiment1 - problems sets for ns102 course

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