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

# Properties of different alcohols used as fuels.

Extracts from this document...

Introduction

TITLE: COMBUSTION OF ALCOHOLS AS FUELS. * DESIGN Question: How is enthalpy change affected by the molecular structure of alcohols and which is comparatively a more suitable fuel? The hypothesis I will be making is that the enthalpy of combustion of the alcohols will increase as the length of the alcohol chain increases i.e. the addition of a CH2 group. In a chemical reaction, the bonds between atoms in the reactant side break down to form new bonds in the products. When alcohols are combusted, the covalent bonds break up to form new bonds. The energy released when bonds are formed is more than the energy absorbed when bonds are broken which implies that enthalpy change reactions are exothermic reactions since heat is given out and therefore the value of the enthalpy change will be negative. Therefore, when there are more atoms, more bonds are broken and hence more bonds are made. Enthalpy change of combustion of alcohols is therefore affected by molecular structure as it takes more energy to break and make bonds when the number of atoms is increases than the energy needed when the number of atoms is comparatively lower. Finally, the fuel that has the highest enthalpy change should be comparatively more effective as a fuel. Variables: - Independent variables: 1. Propanol 2. Butanol 3. Pentanol 4. Hexanol - Dependent variables: - Controlled variables: 1. ...read more.

Middle

11. Next, we find the number of moles combusted using the formula No. of moles = m/Mr where m = the mass of the alcohol used and Mr = molecular mass of the compound. 12. If we divide the value of the heat absorbed by the water by the number of moles (n), we get the enthalpy change of combustion of the alcohol i.e. ?H = Q/n. 13. Next we check which alcohol has the highest enthalpy change of combustion and evaluate our hypothesis. Note: The above method should be repeated twice for each of the four alcohols. * DATA COLLECTION AND PROCESSING. Results table: Alcohol used. Mass (g) of spirit lamp. (before lighting) Mass (g) of spirit lamp. (after putting off) Mass (g) of alcohol used. Average mass of alcohol used. (g) Propanol 170.15 169.24 0.91 0.95 169.24 168.25 0.99 Butanol 136.23 135-53 0.70 0.725 135.53 134.78 0.75 Pentanol 137.11 136.49 0.62 0.61 135.28 134.68 0.60 Hexanol 189.01 188.43 0.58 0.565 188.40 187.85 0.55 Calculations: Amount of heat absorbed by water: Q = mc?T = 0.05 x 4.18 x 30 = 6.27 KJ. Propanol: Mass of alcohol used = 0.95g. Molecular Mass = 60.1 g. Therefore, number of moles = 0.95/60.1 = 0.01580 moles. Enthalpy change (?H) = 6.27/0.01580 = -396.84 KJ/mol. % error = (Theoretical value - experiment value) x 100 Theoretical value = 2021 - 396.84 x 100 2021 = 80.00% error. ...read more.

Conclusion

Therefore, complete combustion does not take place. ==> The alcohol containers had varying sizes of wicks and amount of alcohol in them. Therefore, the flame was varying in size and was one of the sources of the error. ==> Some of the alcohol might be evaporating from the spirit lamp. ==> The thermometer might have touched the bottom of the calorimeter giving inaccurate results. ==> Another possibility could be lack of oxygen in the room which led to incomplete combustion as oxygen molecules would react with only one carbon molecule to from carbon monoxide, CO which is a poisonous gas since limited supply of oxygen causes some carbon atoms get released before they react with oxygen and hence might be present in the calorimeter in the form of soot. Improvements: ==> Use of a heat insulator such as heatproof mats to minimize heat loss and using an air tight around the spirit lamp to prevent any amount alcohol from evaporating. ==> Make sure the bob of the thermometer does not touch the extreme bottom of the calorimeter and the water is stirred throughout the experiment. ==> Make sure that a sufficient supply of oxygen is available; the experiment takes place in an area where there is free air circulation. ==> Similar spirit lamps are used having the same width of the wick so that the flame can reach the calorimeter regardless of the alcohol used. ==> Use of more advanced equipment. ?? ?? ?? ?? ...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

# Related International Baccalaureate Chemistry essays

1. ## The Enthalpy of Neutralization

+ H2O(l) -57.6 kJ�mol-1 -53.3 kJ�mol-1 NaOH(aq) + H2SO4(aq)--> NaSO4(aq) + H2O(l) (2.00mol�dm-3 NaOH) -57.3 kJ�mol-1 1 -51.2 kJ�mol-1 NaOH(aq) + H2SO4(aq)--> NaSO4(aq) + H2O(l) (4.00mol�dm-3NaOH) -57.3 kJ�mol-1 1 -58.5 kJ�mol-1 1: I looked all over the internet and couldn't find a solid answer or source to take an accepted value of enthalpy of neutralization for these reactions.

2. ## Thermodynamics: Enthalpy of Neutralization and Calorimetry

C� 95.7 �.5 C� Final Temperature 25.2 �.5 C� 24.9 �.5 C� 25.3 �.5 C� Specific Heat of Cylinder .225 �?.001?cal/gC� .221 cal/gC� .213 cal/gC� .220cal/gC� The Neutralization of NaOH with Hcl - table 3 Trial 1 Trial 2 Trial 3 Measured Average Mass of Calorimeter 7.921 g 7.803 g

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

�mass of water= mass of acid (diluted) That is, we say, that the density is 1.0g/cm3 even though it is not water Now, mass = density* volume So when the density is 1 g/cm3, then mass is equal to volume. �specific heat capacity of water= 4200 J/kg �C (data booklet)

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

Molar mass vs. Heat of Combustion (average trend): Graph 2. Molar Mass vs. Molar Heat of Combustion (max and min trend line): Graph 3. Accepted Values for Molar Heat of Combustion Table 11. Percentage difference of experimental values from experimented values: Alcohol Average Molar Heat of Combustion (kJ mol-1)

1. ## Dissolved Oxygen in water

Step 5: Let the sample stand and the flocculent precipitate will start to settle. 10. Step 6: After approximately 2 minutes, when the upper half of the bottle becomes limpid, add 10 drops of Sulphuric acid solution. 11. Step 7: Again stopper the bottle and invert it until all particulate material is dissolved.

2. ## Bomb calorimetry. The goal of this experiment was to use temperature data over ...

0 - 0 = 8.0 oC = 281K For naphthalene, â T= 23.2 – 15.5 – 0 - 0 = 7.7 oC = 280.7K The eq. (7) rearranges to CV = (âcUbenzoic acid+ âcUcotton)/(- âTbenzoic acid) CV = (-26.434 kJ/g x 0.7408 g– 0.059 kJ)/[- 281 K] = 0.0699 kJ

1. ## Analysis of the Standard Enthalpy of Combustion for Alcohols

5. Stand 6. 2 x clamps 7. Scales 8. 1500 cm3 distilled water 9. Heat proof mat 10. Matches Method: 1. Connect the temperature sensor to the datalogger. Connect the datalogger to the computer. Ensure the datalogging software is loaded and set to record the temperature of the sensor.

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

Measure exactly about 40 cm³ of water and put it into the boiling tube.Weigh out the mass of the alcohol burner containing methanol before the combustion process. 2. Place the alcohol burner containing methanol 3 cm under the boiling tube, measured from the top of the burner. • Over 160,000 pieces
of student written work
• Annotated by
experienced teachers
• Ideas and feedback to
improve your own work 