• Join over 1.2 million students every month
• Accelerate your learning by 29%
• Unlimited access from just £6.99 per month
Page
1. 1
1
2. 2
2
3. 3
3
4. 4
4
5. 5
5
6. 6
6
7. 7
7
8. 8
8
9. 9
9

# Investigating the enthalpy change of different fuels when combusted.

Extracts from this document...

Introduction

Investigating the enthalpy change of different fuels when combusted. Aim: The aim of this experiment is to see how the enthalpy changes vary when different alcohols are combusted in standard conditions. The alcohols used will be: Ethanol, Propan-1-ol, Butan-1-ol, Pentan-1-ol and Hexan-1-ol. These alcohols all have the OH functional group on the first Carbon atom of the molecule. Background Knowledge The enthalpy change of combustion (also shown as ?Hc) is a measure of energy when one mole of a fuel burns completely in air, at a standard temperature and pressure. This standard temperature is 298 Kelvin and 1ATM pressure. Maintaining these conditions would be complicated; therefore the experiment will be carried out in normal conditions. Any drastic alterations to these conditions will need to be taken care of to maintain a degree of accuracy. As combustion is exothermic (heat is transferred to the environment) all of the enthalpy changes will be negative. The formula for enthalpy change is: Energy Transferred= Heat capacity of water x Change in water temp x mass of water. Or E=MC?T Hess's Law. "the enthalpy change for any chemical reaction is independent of the intermediate stages, provided the initial and final conditions are the saeme for each route." This basically means that in an enthalpy cycle, detours can be made to reach the final products and the total energy required for the detour will be equal to the direct route ie. The enthalpy change for ?H1 = ?H2 + ?H3. as we cannot go directly along ?H1, we must take the detour and from this we can calculate the enthalpy change. This can be calculated by the enthalpy changes of combustion for carbon, hydrogen and the alcohol in question. Bond Enthalpies: The amount of energy required to break the bonds between atoms is called the disassociation energy. The higher the disassociation energy, the shorter the bond is in length and the stronger the bond is. Single bonds are relatively easy to break as opposed to double or triple bonds. ...read more.

Middle

fill a copper calorimeter with 100 cm^3 of water 4. note the temperature of the water 5. ignite the spirit burner and wait for temperature to rise by 20�C 6. extinguish the spirit burner once the temperature has risen by 20�C 7. Measure the mass of the spirit burner with lid again. Note mass. 8. Empty and Clean the base of the calorimeter to clear up any soot due to incomplete combustion. 9. repeat the experiment for all alcohols 10. repeat experiment 3x for each alcohol. Safety All of the alcohols used in this experiment are harmful to human health if ingested or if contact with eyes occurs. Ethanol vapours are known to have narcotic properties and could be dangerous if inhaled in moderate volumes. All of the alcohols are irritant to the skin and eyes. To overcome this problem, gloves must be worn when handling alcohols out of the spirit burners and goggles should be worn at all times to prevent irreversible damage to the eyes. Alcohol vapours may have narcotic effects so they should not be inhaled or ingested. All of the alcohols are flammable so should be kept away from sources of ignition and incandescent materials. Ignition of the alcohols should only be completed when all of the equipment is set up and there is no risk of any materials catching fire or melting. Measurements All temperature measurements will be undertaken with either a thermometer or a data logger. The data logger is digital and therefore more accurate. These can show how much the temperature has changed and can provide a signal to extinguish the flame of the spirit burner. To maintain a degree of accuracy, all experiments should be carried out at least three times and an average should then be taken. If the mass changes are more than 5% away from each other, the experiment should be retaken to get more accurate results. ...read more.

Conclusion

This layer of soot acts as an insulator to the heat and increases the number of moles of fuel required to heat the water. The above factors all significantly affected the results due to heat loss. There were other contributing factors to the large difference between predicted and actual results. The distances that the wick stuck out from the top of the burner were all equal, but some of the wicks had differing diameters and amount of fraying at the end of the wick. Both of the factors caused there to be differing surface areas that could contain fuel for combusting. The diameter of the wick caused there to be larger or smaller surface areas through which the fuel could be combusted and the fraying increased the surface area drastically, as each fibre from the wick was fully exposed at the end. This cased there to be more or less fuel burned across the different fuels. The larger flames were in contact with the base of the calorimeter and on one occasion were large enough to ignite the tin foil covered card that was insulating the top of the calorimeter, whereas the smaller flames were barely reaching 5cm from the tip of the wick. This caused there to be more fuel burnt and more heat lost due to flames escaping from the insulation for the larger flames, and more fuel being burnt due to the distance between tip of flame and calorimeter. There is also a degree of uncertainty. This is calculated by using the following formula: Predicted - actual Predicted x100 = uncertainty. Here are the uncertainty values for my results: Predicted (KJ/mol) Actual (KJ/mol) Uncertainty Ethanol 1249 200 83.98719 Propanol 1867 316 83.074451 Butanol 2485 483 80.56338 Pentanol 3103 559 81.985176 Hexanol 3721 594 84.036549 There is a large degree of uncertainty in this experiment caused mostly be the lack of sufficient heat insulation. These figures show that the results are very inaccurate and are relatively useless to science. ?? ?? ?? ?? Luke Harlow Candidate No.: 1109 Centre No.: 20806 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Inorganic 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

# Related AS and A Level Inorganic Chemistry essays

1. ## Investigation to determine the Relative atomic mass of Li

5 star(s)

100cm3 measuring cylinder 0.500 Balance 4.170 25cm3 pipette 0.012 50cm3 burette 0.120 Total 4.802% Thus the actual result with quantitative errors taken into account can be calculated. - 4.802% of calculated mass of Li = 7.21/100 x 4.802% = 0.346 - actual result is 7.21�0.346 - this is between 6.86

2. ## effects Concentration and Temperature on the Rate of Reaction

This ensures that the solutions are kept under the same conditions as each other, and that accurate amounts of solution can be measured out. 50ml Potassium bromate(V) solution Used as part of the reaction. 0.01M Sulphuric acid solution Used as part of the reaction.

1. ## Lab report Determination of Enthalpy Change of Neutralization

to the equation, 1 mole of HCl reacts with 1 mole of NaOH to form 1 mole of H2O. So, No of mole of H2O = 0.05 mol Heat given out per mole of H2O formed = 2567.405812 / 0.05 = 51.3 KJ mol-1 The enthalpy change of neutralization is

2. ## Determination of Chemical Oxygen Demand (COD) of a Given Sample of Waste Water

of FAS used to titrate with excess K2Cr2O7 in the sample is 17.20ml. no. of mole of FAS titrant used to titrate with excess K2Cr2O7 = 0.2502 x 17.20 /1000 = 0.0043 mole mole ratio of Fe2+: Cr2O72- = 6 : 1 hence, no.

1. ## Chemistry - Data Analysis

Once the graphs were plotted gradients were calculated at temperatures of 80�C, 60�C and 50�C to determine the rate at which the temperature was falling. The results obtained are shown in the table below. Degrees(�C) Polystyrene Cup (Minutes) Plastic Cup (Minutes)

2. ## The Chemistry oh Phosphorous

is bone and tooth formation; about 85% of all phosphorus in the body can be found in the bones and teeth13. We store about 750g of phosphorus in our body at any ones time14. Phosphorus in bone exists as the compound calcium phosphate Ca3(PO4)2 and is involved in bone formation

1. ## Energy and Rates Analysis of Chemical Reactions

10. Prepare the three stopwatches. 11. Add a sample of Magnesium to each beaker (be sure to record the exact mass of magnesium being added to each), and simultaneously start the stopwatches. 12. When the magnesium is completely dissolved in the first solution, stop the first watch.

2. ## The purpose of this experiment was to prepare a sample of Aspirin and measure ...

and Calculations Results Mass of Salicylic acid 50.07g Actual Mass of Aspirin 82.81g Colour of precipitate formed White precipitate Melting point 119-122°c The formula equation for this reaction will be used to calculate the number of moles of Aspirin formed which will help calculate the percentage yield.

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