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Exp1: A2-Bomb Calorimeter

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GOAL

Benzene has a bond that proves to be stronger than usual. The underlying effect of this seems to be from the strength given by the resonance.

THEORY

Compare the amount of bonds CDDT (CAS 706-31-0) to benzene and cyclohexane.

Great place to find pymol molecule files: http://webbook.nist.gov/cgi/cbook.cgi?ID=C676222&Mask=4

 

 

Review Halpern Experiment 5 and 6.

It is at constant volume (the calorimeter?).

Energy and enthalpy.

Maybe review Hess’s law.

“The experimental determination of the heat of formation of a material is therefore and important contribution to thermodynamics (Halpern 121).”

“The reaction is initiated by suddenly raising the temperature of the fuel This is accomplished by causing a very hot wire, heated via an electric current to break apart and fall onto the fuel sample. Sometimes, the wire is in contact with the sample (122).” High pressure must be sustained in the reactor.

“The experimental measurable in this reaction is the heat flow under constant volume conditions. From the first law, ΔU = q + w, we have for the case of only gas expansion/compression, or PV work, ΔU = q + ∫Pext dV. Hence, 

ΔU = qv,

and the measured heat flow in the bomb is equal to the change in internal energy for the reaction.= (Halpern 122-123).”

The objective is to determine the enthalpy of the reaction.

We will be using benzoic acid pellets.

Will the results be from finding the C of our calorimeter? Then determining Q of our CDDT combustion triggered by the wire’s external voltage?

ERRORS: incomplete combustion of sample–most likely due to not enough oxygen.

——-

So we have CDDT and cyclohexane. (the benzoic acid is just for calibration).

Calibration
This consists of two runs of benzoic acid combusted fully. (Ideally, should have been more than 3). This is a chemical calibration, described as the second method in Experiment 5 of Halpern’s book.

Calibration setup
A 10 cm wire was wrapped around the electrodes, touched the benzoic acid pellet.

DATA ANALYSIS
Part of this will include both Experiment 5 and 6 in Halpern’s text.

Some good references for linear regression using Excel are here:

  • http://www.ncsu.edu/labwrite/res/gt/gt-reg-home.html

How to plot two trend lines for one chart is best explained here:

  • https://answers.yahoo.com/question/index?qid=20110215101044AAa2Z8y

 

 

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