• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Investigating the enthalpy of combustion

Extracts from this document...

Introduction

Chemistry Lab report - Enthalpy of combustion Aim: To see the trend in the combustion of the first five alkanols. Introduction: The standard enthalpy of combustion is the enthalpy change when one mole of a substance completely reacts with oxygen under standard thermodynamic conditions (although experimental values are usually obtained under different conditions and subsequently adjusted). E.g. The standard enthalpy of combustion of ethane is the energy released when one mole of ethane is completely burned in excess oxygen under standard conditions. i.e. the energy change for the reaction: C2H6 + 3.5 O2 --> 2CO2 + 3H2O By definition, combustion reactions are generally strongly exothermic and so enthalpies of combustion are generally strongly negative. It is commonly denoted as or Enthalpies of combustion are typically measured using bond calorimetry, and have units of energy (typically kJ); strictly speaking, the enthalpy change per mole of substance combusted is the standard molar enthalpy of combustion (which typically would have units of kJ mol-1). ...read more.

Middle

Dependent variable > The dependant variable is the amount of fuel burnt after the 20oC rise in temperature. This can be measured using the Digital balance. Constant > The constant variables in this experiment are the conditions in which the trials were performed. The equipment used is also constant since a change in instrument could cause a variation in the data being recorded. RESULTS MASS - Trial 1 Name of fuel Weight of fuel (g) [�0.01] START-END= Change of mass (g) START END Methanol 257.85 257.02 0.83 Ethanol 233.76 232.96 0.80 Propanol 252.24 251.70 0.54 Butanol 282.14 281.51 0.63 Pentanol 268.10 267.48 0.62 MASS - Trial 2 Name of fuel Weight of fuel (g) [�0.01] START-END= Change of mass (g) START END Methanol 253.85 253.04 0.81 Ethanol 287.72 287.12 0.60 Propanol 269.36 269.00 0.36 Butanol 272.24 271.80 0.44 Pentanol 265.16 264.71 0.45 Name of fuel Calculation for Average mass (T1 + T2)/2 (g) Average mass of fuel burnt (g) ...read more.

Conclusion

From the graph we can see a positive correlation between the length of the hydrocarbon chain and the Heat evolved per mole. Evaluation The experiment was fair and safe since all the safety measure were taken e.g. wearing goggles, handling fuels with care etc. The results were fairly accurate but showed some difference between the two trials due to the following sources of errors. Sources of Errors 1. There was a lot of heat lost to the surrounding and so we could not account for all of the ?H. 2. While measuring the gas after the experiment was over, the weight kept on decreasing the longer you kept on the weighing scale. This is because of the capillary action of the wick of the alcohol container (spirit lamp). 3. The time was not stopped on an exact rise of 200C because the temperature does not rise exactly 200C. 4. There was a slight time lapse between the time of setting up the trial, lighting the spirit lamp, and starting the stop watch ?? ?? ?? ?? Prashant Pradhan YR 11 Chemistry HL - Enthalpy of combustion ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our International Baccalaureate Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related International Baccalaureate Chemistry essays

  1. Hesss Law Lab, use Hesss law to find the enthalpy change of combustion of ...

    The molar enthalpies for both reactions were calculated. Both of these reactions were carried out three times each. The last intermediate reaction was not done because it was almost impossible to carry out that experiment by using the available equipments but instead table values were given for those reactions.

  2. Enthalpy of Combustion Lab Report

    Some black soot was formed on the bottom of the calorimeter after the spirit lamp was placed underneath it in the experimental procedure. 3. It was noted that when the mass of the spirit lamp was noted in the beginning of the experiment, the lamp was not warm.

  1. IB chemistry revision notes

    * Base: a substance that can neutralise an acid (accepts ions) * Alkali: a substance that will release ions into the solution. All alkalis are bases, but no all bases are alkalis. * With indicator Acid Alkaline Litmus -Red -Blue Phenolphtalein -Colourless -Pink Methyl Orange -Red -Yellow * Acid neutralization

  2. Thermodynamics: Enthalpy of Neutralization and Calorimetry

    With this information the Heat Capacity can be calculated through the formula: (m �?T�s)hot = (m �?T � s)cold + (Heat Capacity � ?T). Now with the heat Capacity of the calorimeter, the specific heat of the metal cylinder can be found.

  1. Molar Heat combustion chemistry - investigate the effect of molar mass on the molar ...

    flame was different for each group and each alcohol * The coke cans used were previously used for the same experiment and as a result there was soot (carbon) on the bottom of the can. * The flame flickered due to movements around the apparatus Propanol * The distance between

  2. To determine the standard enthalpy of formation of Magnesium Oxide using Hess Law.

    Step 1: Calculating absolute uncertainty of the value for ΔHX Percentage uncertainty = Apparatus Uncertainty in apparatus Lowest quantity measured Percentage uncertainty Thermometer ±0.25 32.2oC = 0.78 % Burette (50cm3) ±0.10 15.0cm3 = 0.36% Digital Balance (g) ±0.01 0.05g = 20% Total Random Error 0.78 + 0.36 + 20 =

  1. The aim of this experiment is to examine the enthalpy of combustion of the ...

    Light the burner and measure the temperature changes of the water for 120 seconds, every 15 seconds write down the temperature measurement in the previously prepared results table. 4. After 120 seconds turn off the alcohol burner, but keep measuring temperature changes for next 90 seconds and recording them every 15 seconds.

  2. Analysis of the Standard Enthalpy of Combustion for Alcohols

    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 flask walls. 4. Weigh the alcohol lamp (including its cap) using the scales and record the mass.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work