'Analysis of the Standard Enthalpy of Combustion for Alcohols Essay\r'

'Aim:\r\nTo go over the model enthalpy transmute of electrocution for 5 consecutive inebriants in the inebriant homologous series, methanol, ethanol, propan-1-ol, butan-1-ol and pentan-1-ol, by using a calorimetric method to elaborate the commove gained by the hundredcm3 piss system system in the experiment, and hence the heat befogged by the intoxicantic drink lamp at measuring rod temperature and embrace (298 K and 101.3 kPa).\r\nBackground knowledge:\r\nAlcohols are organic compounds containing Oxygen, heat content and one C. The alcohols are a homologous series containing the functional â€OH group. As we coin down the homologous series of alcohols, the function of Carbon atoms increase. Each alcohol molecule differs by â€CH2; a single Carbon atom and two Hydrogen atoms.\r\n fire is the oxidation of carbon copy compounds by oxygen in air to form CO2 and H2O. Combustion produces heat as well as carbon dioxide and peeing system. The enthalpy substitute of combustion is the enthalpy deepen that occurs when 1 mole of a fuel is burnt alone in oxygen.\r\nWhen alcohol undergoes complete combustion it produces carbon dioxide and water as products, and muscle is released. The standard enthalpy of combustion of an alcohol (âH°comb) is the enthalpy substitute when one mole of an alcohol completely reacts with oxygen under standard thermodynamic conditions (temperature of 25°C and pressure of 101.3 kPa). The standard enthalpy remove of combustion of alcohols varies depending on their molecular size. The greater the rate of carbons, the higher the standard enthalpy of combustion, as thither is the presence of much bonds. The larger the alcohol molecule, the more than bonds go awaying be broken and formed, and therefore more heat bequeath be produced. Using experiments, the standard enthalpy of combustion of an alcohol can be found, buy first finding the heat released during the response using the equation\r\nHeat=mass o f water Ãparticular proposition heat capacity of water à hold water in temperature of water\r\nNote: The specific heat capacity of water is 4.18 Jg-1°C-1.\r\nand then finding the number of moles of alcohol burnt, and dividing the heat by this number.\r\nEquipment:\r\n1. 250 cm3 Conical flask\r\n2. 100 cm3 ± 0.08 cm3 pipette\r\n3. Loggerpro thermometer\r\n4. 5 x incompatible consecutive alcohol spirit burners (eg. methanol, ethanol, propanol, butanol and pentanol)\r\n5. provide\r\n6. 2 x fastens\r\n7. Scales\r\n8. 1500 cm3 distilled water\r\n9. Heat demonstration mat\r\n10. Matches\r\nMethod:\r\n1. draw the temperature sensor to the datalogger. Connect the datalogger to the computer. Ensure the datalogging software is loaded and pose to bring down the temperature of the sensor. Set the sampling rate to 1 archetype per second for 210 seconds.\r\n2. Using the pipette, pipette 100 cm3 distilled water into the conelike flask.\r\n3. Set up the stand, and clench the coni cal flask 25 cm from the table. Also clamp the temperature probe 30 cm from the table, so that it is settle in the distilled water but not in contact with the conical flask walls.\r\n4. Weigh the alcohol lamp (including its cap) using the scales and record the mass.\r\n5. Place alcohol lamp instantaneously under the conical flask on a heat proof mat.\r\n6. Click ‘collect’ on datalogger to start recording the temperature. After 30 seconds, motiveless the alcohol lamp.\r\n7. When the datalogger r severallyes 210 seconds immediately extinguish the flame by replacing the cap. ‘Store the latest run’ in loggerpro.\r\n8. Re-weigh the alcohol lamp (including cap) as soon as doable after extinguishing the lamp.\r\n9. Repeat steps 2 †8 with the uniform alcohol to obtain rails 2, and trial 3 results.\r\n10. Repeat steps 2 †9 for 4 other consecutive alcohols.\r\n11. get the average change in mass of severally alcohol and answer for the change in temp erature of water for each trial.\r\n12. Calculate energy fawned by this using q=mcâT then calculate âH°comb=qn\r\n13. Plot the graph of âH°combversus number of carbons in alcohol.\r\nApparatus:\r\ntemperature probe\r\ndatalogger crook\r\n5 cm\r\n25 cm\r\nalcohol lamp\r\nloggerpro collector on computer\r\nheatproof mat\r\n100 cm3 distilled water\r\nconical flask\r\nclamp\r\nclamp\r\nVariables:\r\n1. Independent\r\nThe alcohol used to heat water will be changed, however all alcohols will be primary.\r\nThe range of alcohols will be 5 consecutive alcohols from the homologous series; methanol, ethanol, propan-1-ol, butan-1-ol, pentan-1-ol.\r\n1. Dependent\r\nThe change in temperature of the 100cm3 distilled water when heated by an alcohol lamp.\r\n1. Measure the initial temperature and final temperature using loggerpro. The change in temperature can be calculated by: ÎT=T(final)-T(initial)\r\n1. Controlled\r\nFinding the âH using âH°comb=qn\r\nControlled Varia bles\r\nHow is it controlled?\r\nEffect on experiment if irrepressible\r\nType of liquid\r\nUsing only distilled water for all trials throughout the experiment.\r\n distinct liquids could result in a difference in the strength of loving forces between particles, meaning a different specific heat capacity which would accept the computer science of energy gain to water using the equation q=mcâT, and thus an incorrect enthalpy change value.\r\n deal of liquid used\r\nMeasure 100cm3 of distilled water by using 100 cm3 ± 0.08 cm3 graduated pipette for each trial.\r\nIf the volume was not exactly 100 cm3 it would at present affect the mass of the water which will affect the q=mcâT value and thus the âH value.\r\nMaterial glassware\r\nUse the equal strike out and materials of a conical flask for all trials.\r\nDifferent materials have different conductivity and may absorb more heat from the alcohol lamp, affecting the boilers suit heat absorbed by the distilled water. Using the same material and brand of conical flask ensures that this is the same for each experiment.\r\nTemperature of environment\r\nFor standard enthalpy of combustion, the temperature mustiness be 25°C however in a class get on this is hard to control, so for each experiment the temperature will stay constant at 19°C.\r\nIf the surrounding temperature was to be changing, the distilled water could be losing more, or gaining more heat energy from the surroundings, straight off affecting the temperature change and therefore, q=mcâT and the âH value.\r\nDistance between the conical flask and alcohol lamp\r\nA clamp will be set at a distance of 25 cm from the table, and this the flask will sit at the same height each trial.\r\nIf the distance changes, the heat lost to the surroundings varies and the heat that reaches the bottom of the calorimeter also varies. This will lead to a difference in demonstrate in temperature of water (âT), and therefore an incorrect u nhurriedness for q=mcâT and âH value.\r\nPressure of surroundings\r\nFor standard enthalpy of combustion the pressure must be 1 atm, however in a classroom this is hard to obtain, so all experiments will be done in a room with the same pressure.\r\nMight influence the vapour pressure point, which will affect the q=mcâT value, and thus the âH.\r\nDuration of heating\r\nThe water will be headed for 180 seconds.\r\nThis ensures that all experiments have the same condemnation to heat the water which directly effects the change in temperature and thus the q=mcâT calculation and the âH value.\r\nReferences:\r\nhttp://gandhijkt.org/blog/wp-content/uploads/2011/03/chemistry-sample-lab-report.pdf\r\nhttp://www.ausetute.com.au/heatcomb.html\r\nhttp://www.s-cool.co.uk/a-level/chemistry/chemical-energetics/revise-it/enthalpy-changes\r\n'