Analysis of the Standard Enthalpy of Combustion for Alcohols Essay

AimTo investigate the pattern enthalpy wobble of combustion for 5 consecutive intoxi ignorets in the inebriant homologous serial, methanol, ethanol, propan-1-ol, butan-1-ol and pentan-1-ol, by using a calorimetric method to manoeuvre the soup up gained by the 100cm3 urine system in the examine, and thus the warmness lost by the inebriantic drinkic drink lamp at metre temperature and pressure (298 K and 101.3 kPa).Background KnowledgeAlcohols are organic compounds containing Oxygen, henry and Carbon. The alcoholic beverages are a homologous series containing the functional OH group. As we give out down the homologous series of alcohols, the number of Carbon atoms increase. Each alcohol molecule differs by CH2 a single Carbon atom and deuce Hydrogen atoms.Combustion is the oxidation of carbon compounds by oxygen in air to form CO2 and H2O. Combustion produces hot pants as wholesome as carbon dioxide and water. The enthalpy channel of combustion is the enthalpy kin d that occurs when 1 mole of a fuel is burned completely in oxygen.When alcohol beneathgoes complete combustion it produces carbon dioxide and water as products, and get-up-and-go is released. The regulation enthalpy of combustion of an alcohol (Hcomb) is the enthalpy change when one mole of an alcohol completely reacts with oxygen under standard thermodynamic conditions (temperature of 25C and pressure of 101.3 kPa). The standard enthalpy change of combustion of alcohols varies depending on their molecular size. The greater the number of carbons, the higher the standard enthalpy of combustion, as there is the presence of more bonds. The larger the alcohol molecule, the more bonds give be broken and formed, and therefore more vex ordain be produced. Using experiments, the standard enthalpy of combustion of an alcohol can be found, buy first finding the heat released during the answer using the equationHeat=mass of water precise heat capacity of water rise in temperature of waterNote The specific heat capacity of water is 4.18 Jg-1C-1.and then finding the number of moles of alcohol burnt, and dividing the heat by this number.Equipment1. 250 cm3 Conical flaskful2. 100 cm3 0.08 cm3 pipette3. Loggerpro thermometer4. 5 x different consecutive alcohol spirit burners (eg. methanol, ethanol, propanol, butanol and pentanol)5. concentrate6. 2 x clenchs7. Scales8. 1500 cm3 distilled water9. Heat proof mat10. Matches mode1. Connect the temperature sensor to the datalogger. Connect the datalogger to the computer. Ensure the datalogging software is loaded and delimitate to record the temperature of the sensor. Set the sampling rate to 1 sample per blink of an eye for 210 seconds.2. Using the pipette, pipette 100 cm3 distilled water into the conic flask.3. Set up the stand, and clamp the conical flask 25 cm from the table. Also clamp the temperature probe 30 cm from the table, so that it is submerged in the distilled water but not in contact with the conical f lask walls.4. study the alcohol lamp (including its cap) using the scales and record the mass.5. Place alcohol lamp instanter under the conical flask on a heat proof mat.6. blackguard collect on datalogger to start recording the temperature. After 30 seconds, timid the alcohol lamp.7. When the datalogger reaches 210 seconds immediately extinguish the flame by replacing the cap. instal the latest run in loggerpro.8. Re-weigh the alcohol lamp (including cap) as soon as possible after extinguishing the lamp.9. geminate steps 2 8 with the alike(p) alcohol to obtain trail 2, and trial 3 results.10. Repeat steps 2 9 for 4 other consecutive alcohols.11. prefigure the average change in mass of each alcohol and calculate the change in temperature of water for each trial.12. Calculate energy draped by this using q=mcT then calculate Hcomb=qn13. Plot the graph of Hcombversus number of carbons in alcohol. appliancetemperature probedatalogger device5 cm25 cmalcohol lamploggerpro colle ctor on computerheatproof mat100 cm3 distilled waterconical flaskclampclampVariables1. IndependentThe alcohol used to heat water will be changed, notwithstanding all alcohols will be primary.The range of alcohols will be 5 consecutive alcohols from the homologous series methanol, ethanol, propan-1-ol, butan-1-ol, pentan-1-ol.1. DependentThe change in temperature of the 100cm3 distilled water when heated by an alcohol lamp.1. Measure the initial temperature and final temperature using loggerpro. The change in temperature can be calculated by T=T(final)-T(initial)1. ControlledFinding the H using Hcomb=qnControlled VariablesHow is it controlled?Effect on experiment if uncontrolled typesetters case of smoothUsing only distilled water for all trials throughout the experiment. different liquids could result in a difference in the strength of cunning forces amid particles, meaning a different specific heat capacity which would guess the calculation of energy gain to water using the eq uation q=mcT, and thus an incorrect enthalpy change value.Volume of liquid usedMeasure 100cm3 of distilled water by using 100 cm3 0.08 cm3 gradatory pipette for each trial.If the volume was not exactly 100 cm3 it would at one time affect the mass of the water which will affect the q=mcT value and thus the H value.Material glasswareUse the corresponding brand and materials of a conical flask for all trials.Different materials postulate different conductivity and may absorb more heat from the alcohol lamp, affecting the overall heat absorbed by the distilled water. Using the same material and brand of conical flask ensures that this is the same for each experiment.Temperature of surroundFor standard enthalpy of combustion, the temperature must be 25C however in a class way of life this is hard to control, so for each experiment the temperature will stay constant at 19C.If the surrounding temperature was to be changing, the distilled water could be losing more, or gaining more hea t energy from the surroundings, directly affecting the temperature change and therefore, q=mcT and the H value.Distance between the conical flask and alcohol lampA clamp will be set at a aloofness of 25 cm from the table, and this the flask will sit at the same height each trial.If 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 rise in temperature of water (T), and therefore an incorrect calculation for q=mcT and H value. hale of surroundingsFor 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.Might influence the vapour pressure point, which will affect the q=mcT value, and thus the H.Duration of heatingThe water will be headed for 180 seconds.This ensures that all experiments have the same time to heat the water which directly effects the chan ge in temperature and thus the q=mcT calculation and the H value.Referenceshttp//gandhijkt.org/blog/wp-content/uploads/2011/03/chemistry-sample-lab-report.pdfhttp//www.ausetute.com.au/heatcomb.htmlhttp//www.s-cool.co.uk/a-level/chemistry/chemical-energetics/revise-it/enthalpy-changes