skf-exp2

DEPARTMENT OF CHEMISTRY FACULTY OF SCIENCE & MATHEMATICS UNIVERSITI PENDIDIKAN SULTAN IDRIS

PHYSICAL CHEMISTRY I SKF 3013 Laboratory Report Experiment 2 STUDENT’S NAME

& MATRIC NUMBER

1. Ong Suu Wan (D20151070971) (D20151070971) 2. Muhammad Afiq bin Mohammad Dhazari (D20152072019) 3. Yii Yuann Ning (D20152072018)

LECTURER’S NAME

Dr. Aisyah binti Mohamad Sharif

TITLE

Heat of Combustion

OBJECTIVES

1. To determine the calorimeter constant using benzoic acid 2. To determine the heat of combustion of an easily combustible material

APPARATUS AND CHEMICALS

Bomb calorimeter Pallet maker Thermometer (scaled divisions accurate to at least 0.20 0C) Pipette 1.0 cm Volumetric Flask 2 liter Fuse wire Benzoic acid 100 cm3 standardized Na 2CO3 (0,0075 M)  Albumin

PROCEDURE

FLOW CHART

RESULT

Heat of Combustion Benzoic Acid: Time(s) Temperature(0C) 30 23.50 60 24.10 90 24.70 120 25.10 150 25.30 180 25.40 210 25.50 240 25.58 270 25.60 300 25.60 330 25.60 360 25.60 390 25.60 420 25.60 450 25.62 480 25.62 510 25.62 540 25.62 570 25.62 600 25.62 630 25.62 660 25.60 690 25.60 720 25.60 750 25.60 780 25.60 810 25.60 840 25.58 870 25.58 900 25.58

Titration of Benzoic Acid Trials 1st  2nd  3rd 

Volume(ml) 1.7 1.6 1.6

Heat of Combustion Albumin: Time(s) Temperature(0C) 30 23.70 60 24.20 90 25.59 120 25.81 150 26.00 180 26.08 210 26.12 240 26.17 270 26.19 300 26.20 330 26.21 360 26.21 390 26.22 420 26.23 450 26.23 480 26.23 510 26.23 540 26.23 570 26.23 600 26.23 630 26.23 660 26.23 690 26.23 720 26.20 750 26.20 780 26.20 810 26.20 840 26.20 870 26.20 900 26.20 Titration of Albumin Trials 1st  2nd  3rd 

Volume(ml) 11.1 11.6 9.8

CALCULATION

Mole of benzoic acid: =

0.852 122.1 /

= 6.98x10-3 mol Heat released in the formation of benzoic acid: = (6.98x10 -3 mol) (13800cal/mol) = 96.324 cal Heat released in the combustion of fuse wire: = (6.98x10 -3 mol) (1400cal/mol) = 9.772 cal Calorimeter constant; W= =

+1+2 ∆ (6318 /)(0.852 ) + 13800 / +1400 / 2.08º 

= 8.90 kJ/ºC Heat of combustion; e2 =

 +1

= (6318

(8.90 /º )(2.08º ) /)(0.852) + 13800 /

= 9.65x10-4 cal/g

Comparison: m= =

26.454  26.454 6318 /

= 4.19x10-3 cal/g

Therefore, 4.19x10 -3 cal/g ˃ 9.65x10 -4 cal/g

Mole of albumin: =

1.034 66000 /

= 1.57x10-5 mol Heat released in the formation of benzoic acid: = (1.57x10 -5 mol) (13800cal/mol) = 0.217 cal

Heat released in the combustion of fuse wire: = (1.57x10 -5 mol) (1400cal/mol) = 0.022 cal

Calorimeter constant; +1+2

W=

∆

=

(6318 /)(1.034 ) + 13800 / +1400 / 2.50º 

= 8693.12 kJ/ºC Heat of combustion; e2 =

 +1

= (6318

(8693.12 /º )(2.50º ) /)(1.034) + 13800 /

= 1.07 cal/g Comparison: m= =

26.454  26.454 6318 /

= 4.19x10-3 cal/g

Therefore, 4.19x10 -3 cal/g ˂ 1.07 cal/g

DISCUSSION

The bomb calorimeter is a very useful tool to have in the lab. It allows us to discover the thermodynamic properties of a substance that is unknown. It accomplishes this by running a known substance in the bomb such as benzoic acid and then comparing the values of the unknown substance such as albumin. The graphs show is what to be expected. They begin with a stable temperature before ignition and a rapid increase after ignition is started. Eventually the graph settles back to an even temperature that is higher than the starting temperature. This behaviour occurs because of the nature of a combustion reaction. As the material is being combusted bonds are breaking and this requires energy to be released in the form of thermal energy. This energy is then transferred to the water and the temperature is registered and recorded. Also, albumin displayed higher values of energy than benzoic acid due to its structure. Albumin is a complex organic ring structure with carbon bonds that more difficult to break than the carbon oxygen bonds of the acid. This leads to greater energy needed to break the bonds and a greater energy released as heat. Therefore, the albumin creates more heat than benzoic acid during combustion. CONCLUSION

The calorimeter constant using benzoic acid is 8.90 kJ/ºC. The heat of combustion of an easily combustible material; albumin is 1.07 cal/g. REFERENCES

Bomb Calorimetry (2005). Retrieved 27 th November 2016 from http://ww2.valdosta.edu/~jaeichle/bomb%5b1%5d.htm

Constant Volume Calorimetry. Retrieved 27 th November 2016 from http://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/ Thermodynamics/Calorimetry/Constant_Volume_Calorimetry