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The following investigation is to discover how much energy it takes to break the carbon and hydrogen bonds in Pentane, paraffin Hexane and Heptane.

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Introduction

Fuels investigation The following investigation is to discover how much energy it takes to break the carbon and hydrogen bonds in Pentane, paraffin Hexane and Heptane. Prediction I predict that the fuel with the most bonds will produce the most amount of energy. The scientific proof that I have behind this is that when bonds are broken and they reform energy is released so if there are more bonds then more energy can be released when they reform. Here are the theoretical values for the energy required to break these bonds. Heptane C7H16+ O2 7 CO2+8 H2O Bonds Broken Energy per bond (KJ Mol-1) Total bond Energy (KJ Mol-1) (C-C) 6 + 347 + 2082 (C-H) 16 + 413 + 6608 (O-O) 11 + 498.3 + 5481.3 Bonds Broken Energy per bond (KJ Mol-1) Total bond Energy (KJ Mol-1) (C=O) 14 - 805 - 11270 (O-H) 16 - 464 - 7427 Total energy required for bond breaking (KJ Mol-1) - 18697 Total energy required for bond breaking (KJ Mol-1) + 14117.3 Bond breaking requires energy to break the bonds therefore it is endothermic Bond making requires energy to make the bonds therefore it is exothermic This reaction ...read more.

Middle

C-H 413 12 4956 C-C 347 4 1388 O=O 498 8 3984 C=O 803 10 8030 H-O 464 12 5568 Total energy in 10328 total out 13598 Net energy change =155983+-3270KJ/mol Paraffin C10 H22+20CO2 +22H2O Type of Bond Bond energy Bonds broken Energy in KJ/mol Bonds made Energy out in KJ/mol C-H 413 44 18172 C-C 347 19 6593 O=O 498 31 15438 C=O 803 40 32120 H=O 464 44 20416 Total energy in 40203 Total out 52536 Total net energy change =40203-52536=-12333 Volume of substance used Starting temp Finishing temp Temperature change Amount of energy released Fuel used 50 292k 345k 53 - 11.08 KJ Mol-1 Hexane 50 292k 343k 51 - 10.66 KJ Mol-1 Heptane Moles of Heptane = 1.46/100 = 0.0146 this is 1/68th of a mole. Moles of Hexane = 1.43/86 = 0.0166 this is 1/60th of a mole. Conclusion My calculated values are well below that of the theoretical ones, this is party because of experimental errors that I will comment on later but the major factor was that the compounds did not combust completely, there was soot in the bottom of the conical flask therefore the alkenes when broken down did not ...read more.

Conclusion

Evaluation During this experiment no seriously hazardous materials were used so a minimum amount of safety equipment but what was used is listed in the equipment list. The procedure was seriously flawed as there was many ways for the heat energy to escape. There was nothing restricting wind therefore the flame was not concentrated on the centre of the conical flask which itself became covered in soot blocking some of the heat energy, due to the conical flask being made of glass this also absorbed some of the energy. Although we weighted the burners before and after the experiment the compounds evaporate very easily in air, which may have affected this weight as well as the five-second period in which the flame was still burning this would reduce the accuracy of the overall experiment. The easiest way to remove the limitations would be to use a sealed burner unfortunately we still have to use a spirit burner. There we two major anomalies in this experiment but both were due to human error more careful procedures would eliminate this, all in all with the improvements mentioned above and completing the experiment in standard conditions would the accuracy of these results would be greatly improved. ...read more.

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