CHM 2046 Chapter Notes - Chapter 13: Rate Equation, Activation Energy, Arrhenius Equation

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18 Mar 2016

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Rate of a chemical reaction- how fast the reaction occurs (m*s) Initial, average, and instantaneous rates: average rate- any two points of time on the graph, instantaneous rate- slope of the tangent line at a certain point. Rate refers to the initial rate: depends on concentration and temperature, the reactant concentration decreases with time b/c they are consumed, the product concentration increases with time b/c products are formed. 13. 3 the rate law: the effect of concentration on reaction rate. Rates are proportionately related to state of matter, temperature, and concentration. Rate law: rate = k[a]m[b]n: the exponents can only be 0-3, units for k is determined after the rate law is solved. Overall reaction order- the sum of the reaction orders (the exponents: 2 = second order. **the order of a reaction and rate law can only be determined by experiment. 13. 4 the integrated rate law: the dependence of concentration on time.

Related Questions

Did the reaction actually stop when the blue-black color appeared? Explain briefly

EXPERIMENT 16 A Kinetic Study of an Iodine Clock Reaction OBJECTIVES: To measure experimental reaction rates under different conditions. To use the method of initial rates to determine the order of reaction. To determine the rate constant of a reaction at different temperatures. To determine the activation energy of a reaction using graphical techniques. rate law. To make deductions regarding a reaction mechanism, based on the INTRODUCTION: According to chemical kinetics, it is possible to write down a Rate Law' for any chemical equation: Rate k[A]m [B] This rate law can be used to calculate the rate at which that particular reaction will proceed when a given concentration' of [A] and [B] are present in the system. However, to do this we must know the value of (it is temperature dependent). k rate constant m order with respect to concentration of A. n order with respect to concentration of B. It is important to realize that the values of k, m and n cannot be determined by looking at the chemical equation. They must be deduced experimentally someone must actually run and time the reaction under varying conditions. In this lab, we will studythe Rate Law forthe following reaction between the persulfate ion,s2os and the iodide ion. General Rate Lane. Rate -k ]m [s20g2-1n This reaction is called a clock reaction b of the thiosulfatestarch indicator system we use to time the reaction. Every you run this reaction, your flask will contain an indicator system consisting of time 5.0 x 105 moles of thiosulfate' ions, S2032, and a little starch. When the two reactants, Ose are first mixed start the reaction, every molecule of I2 that is produced reacts immediately with any nt according to the following chemical equation. S2032-preset 21- S40 12 2 S203 This removes the first 2,5 x 10 s moles I2 (look at stoichiometry of reactions above) from the system but then the thiosulfate is gone. This point is marked by the almost instantaneous appearance of an intense blue-black Also called Rate Equation and Rate Law Expression square brackets around anything, [X], means moles per liter of Xor molarin of x. You pipet 100 ml of 0.0050 M Naasio, into each flask.

Iodine Clock Kinetics?
A
1. In one type of Iodine Clock experiment 5.0 mL each of 0.010 MKI,
0.001 M Na2S2O3, H2O, 0.040 M KBrO3, and 0.10 M HCl are mixed.Calculate
the concentrations of BrO3- and I- immediately after mixing butbefore reaction
(i.e. the initial concentrations of these reactants).

2.Calculate the initial concentration of S2O32- in question#1.

3.In the above experiment, BrO3- reacts with I- to form I2. Thenthe I2
immediately reacts with S2O32- to reform I-. When the S2O32- isused up, the I2 is
no longer converted back to I- and therefore combines with thestarch to cause a
color change. Given the following reactions, calculate the amountof BrO3-
consumed, in moles, when the color change takes place in question#1, (i.e. when
all the S2O32- is consumed).

6I- (aq) + BrO3- (aq) + 6 H+ (aq) ? 3 I2 (aq) + Br- (aq) + 3 H2O(l)
I2 (aq) + 2 S2O32- (aq) ? 2 I- (aq) + S2O62- (aq)

B REaction Rates mixing flasks and noting change in color
Flask 1 Flask2
.10 M KI .0010 M S2O3- H2O .04MBrO3 .01M HCl Starch
32(c) 10ML 10mL 15mL 5mL 10mL 3-4 drops
35(c) 10mL 10mL 15mL 5mL 10mL "
20(c) 10mL 10mL 15mL 5mL 10mL "

Temperature variable and rate of reaction time
32(c) Time(s) 264
35(c) Time(s) 140
20(c) Time(s) 289

find activation energy and frequency factor with above experiment

CHM 2046 Chapter Notes - Chapter 13: Rate Equation, Activation Energy, Arrhenius Equation

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