Affects of Temperature

The Affects of Temperature, Catalyst, and Concentration on Reaction Rate

Abstract

The rate of reaction of iodide and sulfate is drastically affected by enzymes. The enzyme used caused the second most change between temperature concentration and the enzyme. The most drastic change of most reactions is the temperature. The higher the temperature the faster, it only took about 9.77 seconds for the reaction to reach equilibrium when the temperature was 58◦C. compared to 39.05◦C at room temperature with the same concentration. This is important because now we know just how drastically each affects the rate of the reaction. So if we want to speed up or slow down the reaction a certain amount we can.

Introduction

The study of chemical kinetics has to do with the rate of reactions. For a reaction to begin a collision with enough energy to break existing bonds, also called the activation energy, and must be the right orientation. The activation energy of a reaction is determined by the equation ln(k)=-Eₐ/RT+ ln(A), where k is the rate constant, Eₐ is the activation energy, R is the gas constant 8.315 J/mol K, T is temperature in Kelvin. Reaction rates are affected by several factors concentration of each species within the rate law, temperature, and catalysts. The Rate law of any reaction is how the concentration of reactants or products affects the rate of the reaction. This can be determined from the slowest elementary step, called the rate determining step, and cannot be determined from the overall reaction. The rate law equation in this experiment is, Rate of reaction=k[I^1-]^m[S2O8^2-]ⁿ. There are many uses of Reaction rates, for example, when a chemical engineer is running a reaction the reaction needs to move at a reasonable rate. If the rate gets to fast it could over heat or explode, if it is to slow the reaction will take too long for any practical purpose. The chemical engineer controls the rate of the reaction by changing temperature, concentration, and adding or taking out enzymes. In this experiment the rate of reaction of iodine (-1) and sulfur (+7) reacting to form iodine (0) and sulfur (+3) is studied. This is done by timing the how long it takes for the color of iodine to show up after mixing the two. Each solution used is given in table 1 below. The mixes of each solution is given in table 2. To determine the effect of the concentration of each reactant the concentration of each is lowered while keeping the overall volume the same by substituting water containing a chemical that will not affect the reaction. Also in the 8th run of experiment A a drop of the catalyst CuSo4 is added to study the effect to the reaction. In the second experiment the temperature of the solution is changed to study the effects of temperature on the rate of the reaction. The contents of each run in experiment B remain constant while the temperature is changed between 5◦C,35◦C, and 50◦C.

Materials and Methods of Procedure

In experiment A each volume of the different solutions a-e should be measured as indicated in table 2 in experiments 1a-8 by a graduated cylinder. In experiment 8 solution f should be measured by a dropper adding 1 drop to the solution, Solution a-d being placed in one Erlenmeyer flask and solution e in a separate Erlenmeyer flask. Obtain a stop watch to measure the time of the reaction. Quickly mix the two flasks and begin the stop watch and stop it when the solution begins to turn purple and write down the time. Repeat these procedures for funs 1a-8 measuring the temp after the purple shows. In experiment B refer to table 2, run 1 and make 3 identical solutions. Repeat the procedure from experiment A. Obtain a hot plate and heat up a flask of water while placing the first solution in the hot bath and measure the temperature till it reaches the appropriate temperature as indicated in table 3 repeat this for each of the 3 runs.

Table 1: Solution key

Solution Letter

Solution Contents

a

0.200 M KI

b

0.00500 M Na2S2O3 in 0.4% starch solution

c

0.200 M KCl

d

0.100 M K2SO4

e

0.100 M K2S2O8

f

0.100 M CuSO4

Table 2: Solution by run

Run # (mL of solution)

Soln. Letter

1a

1b

1c

1d

2

3

4

5

6

7

8

a

20.0

20.0

20.0

20.0

15.0

10.0

5.0

20.0

20.0

20.0

20.0

b

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

10.0

c

-

-

-

-

5.0

10.0

15.0

-

-

-

-

d

-

-

-

-

-

-

-

5.0

10.0

15.0

-

e

20.0

20.0

20.0

20.0

20.0

20.0

20.0

15.0

10.0

5.0

20.0

f

-

-

-

-

-

-

-

-

-

-

1 drp

Results

Table 3: Experiment A: Concentration effects on reaction rate.

Run #

[I^1-]

[S2O8^2-]

Time (s)

1/Time

Temp(◦C)

Log[I^1-]

Log[S2O8^2-]

Log(time)

1a

0.08

0.04

38.37

0.026

25.2

-1.10

-1.40

1.58

1b

0.08

0.04

40.28

0.025

25.2

-1.10

-1.40

1.61

1c

0.08

0.04

38.38

0.026

25.2

-1.10

-1.40

1.58

1d

0.08

0.04

39.16

0.0255

25.2

-1.10

-1.40

1.59

1 avg.

0.08

0.04

39.05

0.0256

25.2

-1.10

-1.40

1.59

2

0.06

0.04

48.84

0.0205

25.2

-1.22

-1.40

1.69

3

0.04

0.04

52.41

0.0191

25.2

-1.398

-1.40

1.72

4

0.02

0.04

57.34

0.0174

25.2

-1.70

-1.40

1.76

5

0.08

0.03

51.09

0.0196

25.2

-1.10

-1.52

1.71

6

0.08

0.02

1:06.28

0.0151

25.2

-1.10

-1.15

1.82

7

0.08

0.01

2:49.90

0.0059

25.2

-1.10

-2.00

2.23

8

0.08

0.04

17.15

0.0583

25.2

-1.10

-1.40

1.23

Table 4: Experiment B: Temperature's Effect on Reaction Rate

Run #

Time Of Reaction (Sec)

1/Time (S^‾1)

ln(1/Time)

Temp. (◦C)

Temp. (K)

1/Temp (K^‾1)

1 avg.

39.05

0.0256

-3.67

25.2

298.2

3.35*10^-3

1e

25.6

3.90*10^-2

-3.24

35.2◦C

308.2

3.24*10^-3

2f

9.76

0.102

-2.28

58◦C

331

3.02*10^-3

3g

2:28.2

6.75*10^-3

-4.99

1.9◦C

274.9

3.64

Calculations

L of reactant/Total L *M of reactant=M I- or S2O8

Ln(k)=-Eₐ/RT+ln(A)

Rate=k[I-]^m[S2O8]^n

Temp C+273= temp kelven

38.38-39.05/39.05 *100=1.7% 39.16-39.05/39.05 *100=0.28%

40.28-39.05/39.05 *100=3.15% 38.37-39.05/39.05 *100=1.74%

1.7+0.28+1.74+3.15=6.87/4=1.72% deviation

Discussion

In the [I-] vs. 1/time graph shows that [I-] concentration and reaction rate is proportional and the second graph shows that [S2O8] is not proportional to the reaction rate. The concentration of KI decrease increases the time of the reaction. This shows that KI has an order of 2. Also by decreasing the concentration of K2S2O8 the reaction takes about twice as long. This gives a reaction order of 2 to K2S2O8. The overall reaction order is 4. Run 8 with the catalyst CuSO4 are proven to drastically increase the rate of the reaction from an average of 39.05 seconds to 17.15 seconds. Temperature made the biggest difference of the three with the reaction time at 9.77 seconds compared to 39.05 seconds at room temperature with the same concentration.

Conclusion

In the end the experiment accepted the hypothesis that reaction rate is effected by temperature, catalyst, and concentration; with temperature effecting the reaction rate the most compared to the other two. The rate of reaction of iodide and sulfate is drastically affected by enzymes. The enzyme used caused the second most change between temperature concentration and the enzyme. The most drastic change of most reactions is the temperature. The higher the temperature the faster, it only took about 9.77 seconds for the reaction to reach equilibrium when the temperature was 58◦C. compared to 39.05◦C at room temperature with the same concentration. This is important because now we know just how drastically each affects the rate of the reaction. So if we want to speed up or slow down the reaction a certain amount we can.

Works Cited and Bibliography

http://www-teach.ch.cam.ac.uk/teach/IA/KCR_full.pdf

http://pages.towson.edu/ladon/kinetics.html

Lab

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