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experiment_four - Iodination of Acetone Experiment Four...

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Iodination of Acetone Experiment Four Chemistry M01B Laboratory Manual pp. 12 Chemical Kinetics: The Iodination of Acetone The rate at which a chemical reaction occurs depends on several factors: the nature of the reaction, the concentrations of the reactants, the temperature, and the presence of possible catalysts. All of these factors can markedly influence the observed rate of reaction. In this experiment, we will study a reaction which, in the vicinity of room temperature, proceeds at a relatively easily measured rate. For a given reaction, the rate typically increases with an increase in the concentration of any reactant. For the reaction aA + bB cC, the rate can be expressed by the following equation, which is called the rate law, rate = k[A] m [B] n (1) where m and n are generally, but not always, integers, 0, 1, 2 or possibly 3; [A] and [B] are the initial concentrations of A and B (ordinarily in moles per liter); and k is the specific rate constant for the reaction. The numbers m and n are called the orders of the reaction with respect to A and B. If m is 1 the reaction is said to be first order with respect to the reactant A. If n is 2 the reaction is second order with respect to reactant B. The overall order is the sum of m and n. In this example, the reaction would be third order overall. The rate of reaction is also significantly dependent on the temperature at which the reaction occurs. An increase in temperature increases the rate, an often cited rule being that a 10 o C rise in temperature will double the rate. This rule is only approximately correct; nevertheless, it is clear that a rise of temperature to say 100 o C could change the rate of a reaction appreciably. As with the concentration, there is a quantitative relationship between reaction rate and temperature. This relation is based on the idea that in order to react, the reactant species must have a certain minimum amount of energy present at the time the reactants collide in the reaction step. This amount of energy, which is typically furnished by the kinetic energy of the species present, is called the activation energy of the reaction. The equation relating the rate constant, k, to the absolute temperature, T, and the activation energy, E a , is ln k = -E a + constant (2) RT where R is the gas constant (8.314 Joules/mole K for E a in Joules per mole). By measuring k at different temperatures we can determine graphically the activation energy for a reaction.
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Iodination of Acetone Experiment Four Chemistry M01B Laboratory Manual pp. 13 In this experiment, we will study the kinetics of the reaction between iodine and acetone in aqueous solution: H 3 C C CH 3 O + I 2 H 3 C C CH 2 I O + H + + I - H + The rate of this reaction is expected to depend on the concentration of hydrogen ion in the solution, a catalyst, as well as the concentrations of the two reactants. By Equation 1, the rate law for this reaction is rate = k [acetone] m [H + ] n [I 2 ] p (3) where m, n, and p are the orders of the reaction with respect to acetone, hydrogen ion,
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experiment_four - Iodination of Acetone Experiment Four...

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