Chem 162 Lab 3

Chemical Kinetics

starting the crystal violet-hydroxide reactionThe objectives of this experiment are to determine:

a) the order of a chemical reaction, with respect to each of the reactants
b) the rate constant
c) the activation energy
d) the effect of a catalyst on the rate, rate constant, and activation energy

In Part I of this experiment, you will use the method of initial rates to determine the four unknown parmeters (k, b, i, and h) that characterize the rate law for the following reaction:

BrO3- (aq) +6 I- (aq) + 6 H3O+ (aq) —› Br- (aq) + 3 I2 (aq) + 9 H2O (l)

Rate= k[BrO3-]b[I-]i[H3O+]h

In this method, the rate of reaction is measured before any of the reactant concentrations change by a significant amount. The rate constant, k, varies with temperature, but b, i, and h, the orders of the reaction with respect to the corresponding reactants, do not. The activation energy will be determined by evaluating how the rate changes with temperature and the effect of adding a catalyst will be investigated.

In Part II of this experiment, you will use the integrated rate approach to determine the three unknown parmeters (k, c, and o) that characterize the rate law for the following reaction between crystal violet (CV+) and sodium hydroxide (OH-):

CV+ (aq) + OH- (aq) —› CVOH (aq)

Rate= k[CV+]c[OH-]o

In this approach, the change in concentration of CV+ as the reaction proceeds will be monitored as a function of time. By plotting the data, you will determine if the order of the reaction with respect to CV+ is zero order (rate = k), first order (rate = k[CV+]) or second order (rate = k[CV+]2. The pseudo-rate-constant (k') will then be examined in order to determine the order of the reaction with respect to OH- and the rate constant (k).

  • Prelab
    • Intro (pdf 338KB, rev 9/30/12)
    • Required Prelab Assignment in Canvas (due Tuesday 7/23 at 11:30 am)
    • Review Materials & Procedure
    • Review Demonstration

 

 

 

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