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Position of Equilibrium * There are many equilibrium mixtures possible for a given chemical reaction, depending on the concentrations of solutions, the pressure of gases and the temperature of the reaction. * The term position of equilibrium can be used to describe a particular set of equilibrium concentrations for a reaction. * If either the temperature, pressure or concentration of one of the substances changes, then the concentrations of all the substances will change until a new position of equilibrium is reached. * Although the rates of the forward reaction and the reverse reaction are at equilibrium, the concentrations of the reactants and the concentrations of the products are rarely the same. * If the forward reaction is nearly complete before the rate of the reverse reaction has increased sufficiently to establish equilibrium, then the position of equilibrium lies towards the right. * If a low amount of the reactants have been converted to the products before equilibrium is reached, then the position of equilibrium lies to the left hand side. * When a reaction reaches equilibrium, it is impossible to tell whether the reaction has started with the reactants or the products. * For example, if you react equal amounts of Hydrogen and Iodine to form Hydrogen Iodide (left), you will end up with the same amount of reactants and products if you had decomposed Hydrogen Iodide (right).

Shifting the Position of equilibrium * The position of equilibrium can be altered by changing: * The temperature. * The concentration of reacting substances. * The pressure of reacting gases. * La Chatelier’s Principle states that If a system is at equilibrium, and a change is made in one of the conditions, then the system responds to counteract the change as much as possible. * Relating this to pressure, temperature, and concentration: * Increasing the pressure will move the position of