• 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
10. 10
10
11. 11
11

# Comparing the Enthalpy chnage of different alcohols

Extracts from this document...

Introduction

Comparing the Enthalpy Change of Combustion of Different Alcohols Aim: Enthalpy change of combustion of an alcohol is a measure of energy transferred when one mole of alcohol burns completely in oxygen. Alcohols are series of organic compounds which all contain an -OH group. The enthalpy change can be calculated by burning the fuel to heat water. It is believed that 4.2J of energy is required to raise the temperature of 1ml of water by 1�C; therefore I will use this theory in my calculations. In this investigation I will use 4 different alcohols to see how the molecular structure is linked to the enthalpy change of combustion of each alcohol. Hypothesis Relying on my previous knowledge, I predict that alcohols with a larger molecular mass will have a greater enthalpy change of combustion than the alcohols with smaller molar mass, meaning the enthalpy change will go up as the carbon number increases. I can support this hypothesis by calculating the enthalpy change of combustion of each alcohol with bond enthalpies. Hess's law states: 'The enthalpy change for any chemical reaction is independent of the intermediate stages, provided the initial and final conditions are the same for each route. The following diagram is called an enthalpy cycle. It shows a reaction where methanol that combusts in air, reacts with oxygen forming carbon dioxide and water. The diagram shows direct and indirect routes: CH3OH(l) ...read more.

Middle

Goggles and a lab coat will be worn throughout the whole experiment to keep my eyes and my skin from being damaged. I will repeat this experiment with each alcohol three times to make sure that my results are reliable. I will then record my results in a table and find an average mass used to heat the water for each. Safety: Methanol is toxic. It can irritate the eyes and mucous membranes. It can also react vigorously with oxidising materials. That is why, to keep safe, me and my fellow students should take care when handling it to make sure it's not spilled since it can react with substances. Also none of us should stay exposed to it for too long to prevent our skin, eyes and mucous membranes being irritated. Ethanol is a highly flammable chemical. Its vapour can easily catch fire; also inhalation may cause narcotic effects. That's why the spirit burners should be kept well away from naked flames and used in well ventilated classrooms. Propanol is also highly flammable and can irritate skin. Therefore, it should be kept away from any naked flames and handled with gloves on, if available. Butanol is harmful and flammable. It can easily catch fire; that is why I should take care when using it, including keeping it away from naked flames. Fair test: To make this investigation a fair test, I will make sure I control various factors. ...read more.

Conclusion

Percentage error: % error = Error x 100 Expected Result Methanol: 42/726.0 = 0.057851239 x 100 = 5.78 % Ethanol: 545.2/1367.3 = 0.398742046 x 100 = 39.87% Propanol: 728.7/2021.0 = 0.360564077 x 100 = 36.05% Butanol: 2005.8/122.2 = 16.41407529 x 100 = 1641.40% EVALUATION Looking at my investigation, I identified a number of limitations that could have led to the errors shown in my results. > Heat could have been lost to the surroundings since there was nothing around the apparatus, where draft excluders could have been placed to prevent that loss. > Since some of the alcohols have toxic fumes, the room had to bee well ventilated for our safety; that could have resulted in heat loss also. > The thermometer was left for me to read which means there could have been a slight human error. An electric thermometer could have been used; which could record the peak temperature, so no errors would be made during the reading taking. > The soot at the bottom of the calorimeter could have been acting as an insulator and stopping the efficient energy transfer. > A conclusion cannot be drawn about every alcohol because none of the isomers were used. > If I was to do this investigation again, I would take into account all the factors mentioned above and also to extend it, I would use a wider variety of alcohols(e.g. up to hexanol) and also try and do it with some isomers(e.g.Propan-2-ol). Fumilola Fawole ...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 Organic 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 Organic Chemistry essays

1. ## Preparation of propanone from propan-2-ol

5 star(s)

Using 2,4-dinitrophenylhydrazine This is used in our experiment. 2,4-DNP reacts with the carbonyl group for a condensation reaction with the elimination of a water molecule. Take propanone as an example, The product formed is a yellow colour precipitate, so we can easily distinguish the presence of C=O group.

2. ## Comparing the enthalpy changes of combustion of different alcohols

3 star(s)

= energy transferred to water (J) � mass of fuel burned (g) = 12540/ 1.14 = 14581 J/g of fuel Propan-2-ol: Energy released (J/g of fuel) = energy transferred to water (J) � mass of fuel burned (g) = 15884/ 1.14 = 13933 J/g of fuel Butan-1-ol: Energy released (J/g of fuel)

1. ## Comparing The Enthalpy Change OfCombustion Of Different Alcohols

Fresh cold water will be used for each experiment in order to keep the start temperature of the water similar and this would also mean that I would have the same system each time. 5. The burner will be removed from under the copper container before the water reaches the target end water temperature of 80-90 degrees Celsius.

2. ## Find the enthalpy change of combustion of a number of alcohol's' so that you ...

I will need to repeat my experiment a number of times and take an average so I am sure of an accurate result. 1. Measure out 200 cm3 of cold water using measuring cylinder, pour into aluminium beaker, this poses no safety risk but must be done carefully as to keep it a fair test.

1. ## The aim of this experiment is to produce Aspirin. This is an estrification in ...

6 + 16 x 3 = 138 Mr of Aspirin (acetylsalicylic acid) = C9H8O4 12 x 9 + 1 x 8 + 16 x 4 = 180 4.0029g of salicylic acid was used. Therefore the amount of acetylsalicylic acid produced should have been Number of moles = mass Mr =

2. ## Comparing the enthalpy changes of combustion of different alcohols

Before I carry out my experiment, I will ensure that each wick of each spirit burner is the same length, which will ensure an equal rate of fuel is burned. I will need Access to a balance to measure the fuel before and after the experiment.

1. ## Investigating the Enthalpy Changes of Combustion of Alcohols.

The apparatus used in the pre-test. (4) PRELIMINARY METHOD (FROM ACTIVITY DF1.2) 1. Put 200 cm3 of water in a copper calorimeter and record it temperature. 2. Support the calorimeter over a spirit burner containing liquid fuel you are going to test.

2. ## The aim of this experiment is to investigate the enthalpy change of combustion for ...

=-5702KJ/mol (bonds formed) H =+4708-5702 =-994KJ/mol Propanol CH3CH2CH2OH H H H H-C-C-C-O-H H H H CH3CH2CH2OH(l)+4.5O2(g) 3CO2(g) +4H2O(g) =7(C-H) + 2(C-C) + C-O + O-H + 4.5(O=O) =6(C=O) + 8(H-O) =7(410) + 2(350) + 360 + 460 + 4.5(496) =6(740) + 8(460) =2870 + 700 + 360 + 460 +2232 =4440 + 3680 =+6622KJ/mol (bonds broken)

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