thermochemisry report

Ainun Najah(3315083228)
5th English report
THERMOCHEMISTRY II

I. Purposes

1. To determine naphthalene burning calor and liquid paraffin with adiabatic calorimeter bomb
2. To determine calor capacity from bomb calorimeter
3. To observe changing which happen in bomb calorimeter

II. Theory
In thermodynamics and physical chemistry, thermochemistry is the study of the energy evolved or absorbed in chemical reactions and any physical transformations, such as melting and boiling. Thermochemistry, generally, is concerned with the energy exchange accompanying transformations, such as mixing, phase transitions, chemical reactions, and including calculations of such quantities as the heat capacity, heat of combustion, heat of formation, enthalpy, and free energy.
The measurement of heat changes is performed using calorimetric, usually an enclosed chamber within which the change to be examined occurs. The temperature of the chamber is monitored either using a thermometer or thermocouple, and the temperature plotted against time to give a graph from which fundamental quantities can be calculated. Modern calorimeters are frequently supplied with automatic devices to provide a quick read-out of information, one example being the DSC or differential scanning calorimeter.
Several thermodynamic definitions are very useful in thermochemistry. A system is the specific portion of the universe that is being studied. Everything outside the system is considered the surrounding or environment. A system may be: an isolated system — when it cannot exchange energy or matter with the surroundings, as with an insulated bomb reactor; a closed system — when it can exchange energy but not matter with the surroundings, as with a steam radiator; an open system — when it can exchange both matter and energy with the surroundings, as with a pot of boiling water.
A system undergoes a process when one of more of its properties changes. A process relates to the change of state. An isothermal (same temperature) process occurs when temperature of the system remains constant. An isobaric (same pressure) process occurs when the pressure of the system remains constant. An adiabatic (no heat exchange)process occurs when no heat exchange occurs.

III. Tools and Materials

Tools
• Adiabatic bomb calorimeter
• Analytic pair of scales
• Stop watch
• Syringe bottle
• Thermometer

Materials
• Water
• Benzoic acid
• Naphthalene
• Paraffin
• Oxygen gas
• Na2CO3 solution
• Red methyl indicator



IV. Procedures
1. Weighing benzoate acid tablet carefully
2. Going into benzoate acid to adiabatic calorimeter bomb and setting heater wire both of electrode
3. Filling up bomb calorimeter with 30 atm of oxygen gas
4. Filling up calorimeter pail with 2 Liters of water (±0,5 grams). Temperature of water in pail made ±1,5o under room temperature
5. Going into pail to calorimeter. Set bomb up in pail
6. Let calorimeter operate about 4-5 minutes. While automatic control arrange temperature of coat in order to balance with water’s temperature of water in pail. Water’s temperature in pail = T
7. Operating electric current to burn sample. Temperature of pail will decreasing in 20 second after burning started
8. Writing down temperature of water in pail in 6th minutes until constant during 2 minutes
9. Open bomb of calorimeter and go bomb out to lost the gases produced from reaction
10. Washing inside of bomb and patch washing product
11. Titrating washing product with Na2CO3 solution by using red methyl indicator
12. Liberating wire heater which not used up and determining wire heater which used up
13. Calculate calor capacity of bomb calorimeter






V. Date Observation
Determining bomb calorimeter capacity with benzoic acid
a) Mass of benzoic acid : 1 g
b) Long of wire heater used up : 3 cm
c) First temperature :30,18oC
d) Last temperature :30,18oC
30,18oC
30,18oC
30,20oC
30,20oC
VI. Calculating
T0 : 30,18oC = 303,18 K
T1 : 30,20oC = 303,20 K
Mass of benzoic acid : 1 g
ΔUT : 26454 J/g
1 cal = 4,2 j/cal
ℓ used up : 3 cm
correction factor : ℓ used up x 2,3 cal/cm x 1,2 Joule/cal = 3 cm x 2,3 cal/cm x 1,2 Joule/cal = 28,98 Joule
ΔUT = (-Ck x ΔT – U): m
-Ck = (ΔUT x m +U): ΔT
-Ck = (26454 Joule/g x 1 g + 28,98 Joule) : 0,02 K = 1324149 Joule/K
Ck = -1324,15 Joule/K
VII. Date Analysis
This experiment purpose to determine bomb calorimeter capacity by using benzoic acid. Benzoic acid which used must in tablet form, it is to make benzoic acid do the reaction entirely when burned. If benzoic acid reacted in powder form, it is probably not all of benzoic acid do reaction. Beside that, it is make placing of those benzoic acid to touch wire heater when burning. So that, burning nor happen.
10 cm platinum wire set on bomb, so that must be touch to benzoic acid. It is done to make wire accompany electric current which will produced fire work and it sign burning reaction begin. Before bomb entered to pail, bomb filled by oxygen ±30 atm. The function of adding this oxygen gas is to help burning in bomb calorimeter, so that benzoic acid burned entirely.
Reaction :
2C6H5COOH + 15 O2(g) →14 CO2(g) + H20
In experiment, benzoic acid not burned entirely, only burned about 0,1 gram, it is caused when adding oxygen. Not all of oxygen enter to bomb because little pipe setting didn’t exactly in the circulation hole of oxygen gas in bomb. Beside that, when flowing electric current, tomb pressed too short time, so that cause acid benzoic didn’t burn entirely.
During burning process, bomb calorimeter is adiabatic. Which no changing of calor happen or Q=0. It is sign that no losing calor to environment or gaining calor from environment. In experiment, no titration reaction done because there was rest of benzoic acid burned.
By calculating, the value of bomb calorimeter capacity which used was -1324,15 KJ/Kelvin. In this calculation, needed correction factor because there was losing calor by wire heater burning. Correction factor wire burned was 28,98 Joule.


VIII. Conclusions
1. Correction factor wire burned was 28,98 Joule
2. Value of bomb calorimeter capacity which used was -1324,15 KJ/Kelvin
3. Reaction which happen : 2C6H5COOH + 15 O2(g) →14 CO2(g) + H20
4. The function of adding this oxygen gas is to help burning in bomb calorimeter, so that benzoic acid burned entirely

IX. Bibliography
Brady, James E. 1999. Kimia Universitas Asas dan Struktur Edisi Kelima Jilid 1. Jakarta: Binarupa Aksara
Chang, Raymond. 2005. Kimia Dasar Konsep-konsep Inti. Jakarta: Erlangga
Keenan, Charles W. 1989. Kimia untuk Universitas Edisi Keenam Jilid 1. Jakarta: Erlangga
Petrucci, RH. 1989. Kimia Dasar Prinsip dan Terapan Modern. Jakarta: Erlangga