ADAMSON UNIVERSITY

College of Engineering

Chemical Engineering Department

Experiment No. 8

CHEMICAL KINETICS

Group No. 1

*CARNIYAN, Evelina Angelica L. 200810529

MANALILI, Bryan Neil T. 200810214

ORALLO, Karen Grace N. 200811873

TORRES, Angelica Grace A. 200813468

Instructor:

Engr. Jerry Olay

Date Performed: Feb. 28, 2011

Date Submitted: March 07, 2011

I. ABSTRACT

Chemical kinetics was applied in this experiment and used to determine the order and activation

energy of the involved reaction. An ignition tube, covered with a cork and fitted with a delivery tube,

was used for the experiment. The experiment is divided into 3 procedures, categorized according to the

factors that affects chemical kinetics .For the first procedure, the concentrations of HCl (1M, 2M, 3M,

4M and 5M) undergone a reaction with a piece of zinc metal, results to yield zinc chloride and hydrogen

gas, while the tip of the delivery tube was faintly immersed in a beaker with water. The rate of the

reactions was determined through the 30 bubbles that will depart from delivery tube. The second

procedure was divided according to increasing temperature, 40°C, 50°C, 60°C and 70°C was used. The

ignition tube with 2M HCl solution was then removed from the water bath after reaching the required

temperature. A piece of zinc metal was dropped to the solution and covered with a cork with delivery

tube. The required time was determined from the 30 bubbles that emerged from the delivery tube.

Copper Nitrate was used as a catalyst for the 3rd procedure. A mixture of HCl and Cu(NO3)2 was used to

test the effect of catalyst in the reaction. Same procedure as the second experiment was conducted. The

data gathered are calculated with the use of “Rate law” and ‘Arrhenius Equation” for the three

procedures.

II. INTRODUCTION

Chemical kinetics is the study and discussion of chemical reactions with respect to reaction

rates, effect of various variables, re-arrangement of atoms, formation of intermediates etc. The four

common variables that influence reaction rate are the concentration of the reactant, temperature,

catalyst, and surface area. In this experiment, differences in concentration, temperature and with a use

of catalyst will be performed. The reaction involved will result in the formation of zinc chloride and

hydrogen gas. The gas evolved will be used as an instrument for the determination and computation of

order or reaction and activation energy.

III. THEORETICAL BACKGROUND

Factors that Affect Reaction Rates

A) Concentration

Increasing the concentration of reactants in solution increases the number of reactant particles

which increases the number of collisions so the reaction rate increases. Increasing the pressure

of a gaseous reaction by adding more reactant gas particles increases the number of collisions

so the reaction rate increases. Increasing the pressure of a gaseous reaction by reducing the

volume of the reaction vessel increases the number of collisions so the reaction rate increases.

B) Temperature

Increasing the temperature of a reaction increases the kinetic energy of the particles which

increases the number of collisions so the reaction rate increases. Increasing the kinetic energy of

reactant particles also means more of the reactant particles will have the minimum amount of

energy required to form products which leads more successful collisions and therefore increases

the reaction rate. Increasing the temperature will increase the reaction rates both endothermic

and exothermic reactions, it will also affect the equilibrium position.

C) Catalyst

A catalyst lowers the activation energy for the reaction so more reactant particles will have the

minimum amount of energy required to form products so the reaction rate increases.

Determination of Order of Reaction

Where:

v= rate

k= rate constant

[A] and [B]= concentration

a= order of reaction with respect to A

b= order of reaction with respect to B

This is called the rate equation for the reaction.

The concentrations of A and B have to be raised to some power to show how they affect the rate of the reaction. These powers are called the orders of reaction with respect to A and B.

If the order of reaction with respect to A is 0 (zero), this means that the concentration of A doesn't affect the rate of reaction. Mathematically, any number raised to the power of zero (x0) is equal to 1. That means that particular term disappears from the rate equation.

The overall order of the reaction is found by adding up the individual orders. For example, if the reaction is first order with respect to both A and B (a = 1 and b = 1), the overall order is 2. We call this an overall second order reaction.

Arrhenius Equation

E a = activation energy R = 8.314 [ J · mol -1 · K -1 ] T = absolute temperature in Kelvin A = pre-exponential or frequency factor A = p · Z, where Z is the collision rate and p is a steric factor. Z turns out to be only weakly dependant on temperature. Thus the frequency factor is a constant, specific for each reaction.

This equation implies that the rate of an uncatalyzed reaction is more affected by temperature than the

rate of a catalyzed reaction. This is because the activation energy of an uncatalyzed reaction is greater

than the activation energy of the corresponding catalyzed reaction. Since the exponential term includes

the activation energy as the numerator and the temperature as the denominator, a smaller activation

energy will have less of an impact on the rate constant compared to a larger activation energy. Hence,

the rate of an uncatalyzed reaction is more affected by temperature changes than a catalyzed reaction.

IV. PROCEDURE

Effect of Concentration

1. 1M, 2M, 3M, 4M and 5M HCl solutions was prepared by serial dilution from a 17M HCl

2. 10 mL of each solution was placed in an ignition tube with a cork stopper fitted with a delivery

tube.

3. A piece of Zn metal was dropped into the HCl solution.

4. The tip of the delivery tube was faintly immersed in a beaker filled with water.

5. The required time was measured through 30 bubbles came out from the tip of the delivery tube.

6. Rate law was formulated to determine the values of k and n.

Effect of Temperature

1. 10 mL of 2M HCl was used and placed in a clean ignition tube.

2. The solution was heated in a water bath until the required temperatures (40°C, 50°C, 60°C and

70°C) reached.

3. The ignition tube was removed from the water bath and a piece of Zn metal was dropped. Then,

fitted with the delivery tube. During the reaction, the tip of the delivery tube was faintly

immersed in a beaker with water.

4. The required time for 30 bubbles that will emerge from the delivery tube was measured.

5. The rate used in the data obtained from procedure A was used to determine the values of k.

6. The log k versus 1/T was plotted and the activation energy of the reaction was determined by

using Arrhenius equation.

Effect of Catalyst

1. A mixture of 10 mL 2M HCl and 2mL 1M Cu(NO3)2 was placed in a clean and dry ignition tube.

2. The solution was heated according to the required temperatures (40°C, 50°C, 60°C and 70°C) in

a water bath.

3. The tube was removed from the water bath, then added with a piece of Zn, and fitted with the

delivery tube.

4. The tip of the delivery tube was faintly immersed in a beaker with water.

5. The values of k were determined from the rate using data obtained from procedure A.

6. Log (k) versus 1/T was plotted and determined Ea for the catalyzed reaction.

V. RESULTS

A. Effect of Concentration

Concentration(M) Time(s) Rate

1 15.03 0.0665 2 13.96 0.0716 3 10.09 0.0991 4 7.30 0.1370 5 5.21 0.1919

k= -0.03135 (2.303) n=1

k= 0.0722

0

0.05

0.1

0.15

0.2

0.25

0 2 4 6

Rat

e

Concentration of HCl (M)

Series1

Linear (Series1)

B. Effect of Temperature

C) T(K) 1/T(K) Time(s) 1/Time(s) K

40 313.15 37.68 0.026 0.0133 50 323.15 34.33 0.029 0.0146 60 333.15 29.21 0.034 0.0171 70 343.15 27.96 0.035 0.0179

Slope= -407.81 Ea= 3390.56 J/mol

Derived formula from Arrhenius Equation: Ea= 8845.76 J/mol

-1.9

-1.88

-1.86

-1.84

-1.82

-1.8

-1.78

-1.76

-1.74

-1.72

0.0028 0.0029 0.003 0.0031 0.0032 0.0033

log

(K)

1/T

Series1

Linear (Series1)

C. Effect of Catalyst

C) T(K) 1/T(K) Time(s) 1/Time(s) K

40 313.15 204 .004900 .0024510 50 323.15 188 .005319 .0026596 60 333.15 174 .005747 .0028740 70 343.15 166 .006024 .0030120

Slope= -365.14 Ea= 3035.78

Derived formula from Arrhenius Equation: Ea= 6137.91 J/mol

-2.62

-2.6

-2.58

-2.56

-2.54

-2.52

-2.5

0.0028 0.0029 0.003 0.0031 0.0032 0.0033

log

(k)

1/T

Series1

Linear (Series1)

VI. DISCUSSION OF RESULTS

The order of the reaction was a 1st order. The result gathered shows that the

higher the concentration will result an increase also in rate of reaction. The effect of

increasing temperature was also shown in the table of data gathered. An increase in

temperature results also an increase in rate of reaction. The activation energy of the

reaction was computed from the slope and from the derived formula from Arrhenius

Equation. It was found that there is 61.67% error between the two. The effect of

catalyst was also tested. A slow reaction was noticed but an increase in reaction rate.

The result shows that the activation energy of uncatalyzed reaction is higher than the

catalyzed reaction. The possible error that contained in this experiment is from the time

estimated from the 30 bubbles that emerged from the delivery tube.

VII. CONCLUSIONS AND RECOMMENDATIONS

The increase in concentration results an increase in reaction rate. This occurrence

explains that more particles of HCL will collide with the particles of zinc metal.

The HCl particle will gain more kinetic energy if there is an increase in temperature. The

HCl particle will have sufficient energy to react resulting in more successful collisions with zinc

metal.

The effect of catalyst inhibits the reaction. It also increases the reaction by providing a

new mechanism that has smaller activation energy. There will be more collisions between the

two reactants.

The reaction does not depend in the size of metal used because the order of Zn is 0. It

means that even though you add more metal, it won’t affect the reaction rate.

For this experiment, the group recommends that the performer must try to gather data

precisely and handle the apparatus carefully. And also, be careful from the chemicals and some

possible hazards.

VIII. LITERATURE CITED

Arrhenius Equation. Retrieved, March 05, 2011 from http://chemwiki.ucdavis.edu/

Physical_Chemistry/Kinetics/Reaction_Rates/Temperature_Dependence_of_Reaction/A

rrhenius_Equation

Orders of Reaction. Retrieved, March 05,2011 from http://www.chemguide.co.uk/

physical/basicrates/orders.html

Reaction Rate. Retrieved, March 05, 2011 from http://www.ausetute.com.au/

reactrate.html

IX. NOMENCLATURE

SAMPLE COMPUTATIONS

A) Effect of Concentration

B) Effect of Temperature

[A] = concentration

Ea = activation energy

k = reaction rate

m = slope

n = order of reaction

R = gas constant

r = rate

Arrhenius Equation:

C) Effect of Catalyst

Arrhenius Equation: