1. Caloric Content of Reese’s
Peanut Butter Cups by Bomb
Calorimetry
Chris Russell, Ralph Eachus, Rashid Aluswaidi

2. Introduction
Purpose: Investigate the caloric content of a Reese’s peanut butter cup
using bomb calorimetery
What is to be investigated?
Does peanut butter or chocolate component contribute more to overall
calories and why?
Is the total caloric value listed on the package correct?

3. Bomb Calorimetry
● Used to determine heat of combustion of hydrocarbons
● The bomb is pressurized to 25-30 atm with oxygen
● The bomb is immersed in water
● The heat produced during the combustion reaction is transferred to
the water
● A small amount of water (1.0 mL) is added to the bomb to ensure
that all of the water formed during combustion is liquid

4. Bomb Calorimetry Continued
The system can be analyzed using the first law of thermodynamics.
The reaction takes place at a constant volume, allowing for the the
following simplification:
∆U = Q
The heat capacity of the calorimeter is found by combusting a
substance with a known heat of combustion. The temperature change
found from the temperature-time plot is then used in the following
equation:
C,calorimeter=(-)([(∆U,sample*m,sample )+(∆U,fuse*∆m,fuse )])/∆T

5. Bomb Calorimetry Continued

6. Bomb Calorimetry Continued
• The internal energy change of a sample can then be determined using
the heat capacity of the calorimeter:
∆U= - C,calorimeter (T,final-T,initial)
• Finally, this energy can be used to calculate the heat of combustion
for a sample:
∆H=∆U+∆n(g)RT

7. Meaning of Caloric Content
Energy in foods is often represented in kilocalories appears on
package as “Calories”
A kilocalorie is the amount of energy to raise 1 kg of water by 1˚C
1 kilocalorie = 4.184 kJ
Caloric content displayed on food package represent statistical
averages over numerous samples and are therefore not always
accurate

8. Composition of Peanut Butter Cups
●Peanut butter
○Protein
○Peanut Oil
●Chocolate
○Sugar
○Cocoa Powder

9. Composition of Peanut Oil

10. Time-Temperature: PB and Choc

11. Time-Temp: PB Components

12. Time-Temp:Choc Components

13. Final Results
Sample ∆n (mol) T60% ΔH (J/g) Δ (±J/g) Caloric
Content (kcal)
Peanut Butter 20.9 26.90 32,162 1775.6 104
Chocolate 3.5 26.99 30,595 1685.6 87.2
Sugar 10 27.33 12,016 1251.7 32.16
Peanut Oil 4.79 27.6 23,857 1738.8 59.2
Protein Powder 20 26.90 11,107 1236.8 27.6
Cocoa Powder 3.5 26.30 7400 1332.3 15.6
Total calories of peanut butter cup = 192 calories
Total calories listed on package = 215 calories

14. Caloric Contribution from Each Component

15. Conclusions
• Both peanut butter and chocolate contribute a significant amount to
overall caloric content.
• Peanut butter gets most of its calories from the fatty acids found in
peanut oil
• Chocolate gets most of its calories from sugar content
• Total calories from burning chocolate and peanut butter 11.1% less
than the label (192 calories vs. 215 calories)
• Some components of both chocolate and peanut butter were not
tested

16. Literature Cited
(1) Milosavljevic, B.H. Lab Packet for CHEM 457 Experimental Physical Chemistry.
2014, 7-1.
(2) Melvin, A. D. Methods and Standards in Bomb Calorimetry. Washington:
Government Printing Office, 1910.