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Chemistry Lab - design

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Introduction

Simple Calorimetry to find the enthalpy of combustion of alcohols Method 1. Measure 50 cm3 of water into the copper can using the measuring cylinder 2. Select a spirit burner containing an alcohol and record the mass 3. Clamp the copper can at a convenient distance so that the spirit burner can sit underneath the copper can. 4. Take the starting temperature of the water. 5. Attach a lid and stirrer through the centre of this and stir continuously when the spirit burner it lit. 6. Light the spirit burner and time for 2 minutes, after this time, snuff out the flame and record the temperature of the water. 7. Re weigh the spirit burner 8. Repeat using the other alcohols and fresh water in the copper can. ...read more.

Middle

Temperature (water) Before After Before After Propanol 243.67 243.30 24.50 61.50 Ethanol 278.65 277.84 24.60 62.60 Methanol 235.78 234.76 25.50 61.30 Octanol 261.28 260.93 25 50 Butanol 250.32 249.86 24.50 55.50 Trial 3 Weight (�0.05g fuel burner) Temperature (water) Before After Before After Propanol 242.24 242.01 25 63.80 Ethanol 278.81 276.87 24.50 62.10 Methanol 235.77 235.18 26 65.50 Octanol 260.59 259.60 25 52.90 Butanol 249.81 249.38 24.50 58.50 Average Weight (�0.05g fuel burner) Temperature (water) Before After Before After Propanol 243.72 242.67 24.97 62.17 Ethanol 278.59 277.75 24.70 62.70 Methanol 235.78 234.56 25.67 63.93 Octanol 261.18 260.61 25.20 52.30 Butanol 250.34 249.86 24.67 58.03 Energy transferred to the water q = mc?T Methanol Temperature change: (63.93 - 25.67) = 38.26?C Mass change: (234.56 - 235.78) ...read more.

Conclusion

= -1.12 Energy transfer: = 7774.8 J = 7774.8 ?1000 q = 7.7748 KJ Enthalpy Change ?H: (-1.12) ?(60gmol-1) = - 0.019mol-1 (7.7748 KJ) ? (- 0.019mol-1) ?H = -409.200 KJmol-1 Propanol 243.72 242.67 24.97 62.17 Ethanol 278.59 277.75 24.70 62.70 Methanol 235.78 234.56 25.67 63.93 Octanol 261.18 260.61 25.20 52.30 Butanol 250.34 249.86 24.67 58.03 Butanol Temperature change: (58.03 - 24.67) = 33.36?C Mass change: (249.86 - 250.34) = -0.48 Energy transfer: q = (50cm3) (4.18JK-1g-1) (33.36 ?C) = 6972.24 J = 6972.24 ?1000 q = 6.9722 KJ Enthalpy Change ?H: (-0.48) ?(74gmol-1) = - 0.006mol-1 (6.9722 KJ) ? (- 0.006mol-1) ?H = -1162.033 KJmol-1 Octanol Temperature change: (52.30 - 25.20) = 27.1?C Mass change: (260.61- 261.18) = -0.57 Energy transfer: q = (50cm3) (4.18JK-1g-1) (27.1 ?C) = 5663.9 J = 5663.9 ?1000 q = 5.6639 KJ Enthalpy Change ?H: (-0.57) ?(130gmol-1) = - 0.004mol-1 (5.6639 KJ) ? (- 0.004mol-1) ?H = -1415.975 KJmol-1 ...read more.

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