• 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
12. 12
12
13. 13
13
14. 14
14
15. 15
15

# Chemistry Investigation - How does chain length affect: &amp;#8710;Hc&amp;egrave; for alcohols?

Extracts from this document...

Introduction

Chemistry Investigation - How does chain length affect: ?Hc? for alcohols? INTRODUCTION: The enthalpy of combustion is the overall energy change, when 1 mole of a named species reacts with the maximum amount of Oxygen in a combustion process. This must take place under the standard conditions, these being 298K and 1 atmosphere of pressure. Combustion is a process involving the breaking and subsequent making of bonds. The breaking of bonds is an endothermic process and the making of these same bonds is exothermic. The difference between the energy in and out dictates that the combustion of alcohols is exothermic overall, as Ein < Eout. Due to the fact that the combustion of alcohols is an exothermic reaction, the products are at a lower energy level than the reactants and therefore the difference in energy (enthalpy) is always negative. The experiment of alcohol combustion is necessary, because it is otherwise impossible to derive enthalpy values. They must be derived from the temperature change in a chemical reaction. This experiment and the enthalpy information it offers is useful in helping us to understand the efficiency of fuels and how we can use these fuels favourably in the chemical industry. AIM: To determine through a mixture of experimentation and theoretical enthalpy mathematics, the effect of chain length on the combustion enthalpy for different alcohols. I also aim to conduct research into the effects of air current and oxygen quantity when experimenting in an uncontrolled environment. The experimental process I have planned will incorporate the use of the heat equation, in order to find the energy released by the alcohols, as below: E (J) = m (g) x c (J�C-1g-1) x ? (�C) E = Energy; m = mass; c = specific heat capacity; ? = temperature. The use of this equation will allow the energy change to be derived for each of the alcohols according to how much of their mass is used when they are combusted with Oxygen fully. ...read more.

Middle

163.09 290.87 191.63 208.53 191.28 End mass (g) 161.67 289.59 191.05 207.93 190.94 Mass difference (g) 1.42 1.28 0.58 0.60 0.34 Start temp. of H20 (oC) 32.00 26.00 26.00 36.00 25.50 End temp. of H20 (oC) 42.00 36.00 26.00 46.00 25.50 Temp. difference (oC) 10.00 10.00 0.00 10.00 0.00 Attempt 4 Start mass (g) 161.67 201.1 191.04 207.81 190.94 End mass (g) 159.70 199.74 190.44 207.22 190.65 Mass difference (g) 1.97 1.36 0.60 0.59 0.29 Start temp. of H20 (oC) 28.50 26.50 26.00 43.00 27.00 End temp. of H20 (oC) 38.50 36.50 26.00 53.00 27.00 Temp. difference (oC) 10.00 10.00 10.00 10.00 10.00 From the original table of results (Fig. 1), which shows only mass changes, it is possible to deduce the moles of fuel used on average. This was done by first taking the average mass of the fuel used over the four attempts to create a fairer display accounting for some variations, and then using the molar formula. By dividing the average mass by the molecular (formula) mass, the number of moles used can be calculated. Figure 2 Methanol Ethanol Propan-1-ol Butan-1-ol Octan-1-ol Average Mass Change 1.82 1.35 0.59 0.53 0.31 Mass of Alcohol (Mr) 32 46 60 74 130 Moles used 0.056875 0.029293 0.009833 0.007128 0.002365 Furthermore by using the derived mole number, the experimental enthalpy can be found. This is done by first using the aforementioned energy equation to work out how much energy was used to heat 100cm3 of water up by 10C taking into account its specific heat capacity. Hence: Energy (E) = Mass (m) x Specific Heat Capacity (c) x Temperature Increase (?) E = 100g x 4.2J�C-1g-1 x 10 (�C) = 42000J In order to work in the desired kJ units, this figure must be divided by 1000. 42000/1000 = 42kJ. Due to the fact that the enthalpy in terms of the reactants is negative, this figure must be represented as a negative change, so that the enthalpy of combustion will have the necessary negative figure. ...read more.

Conclusion

* The green highlight for Butanol start mass at attempt 4 was due to a large decrease from the previous end mass, which could have been due to faulty equipment. However, it was accounted for, due to a lid being left off of the spirit burner. Due to the volatility of alcohols, this mass was a realistic loss. * The blue highlighted figure was anomalous due to the fact that for that single reading, I employed a strategy of double-draught proofing, but then realised this would be unrepeatable, due to the lack of equipment. Therefore, this is the only result to employ such measures. In reference to Appendix D: * Point A The plotting of the Ethanol enthalpy, shows the greatest deviation from the best fit curve. Yet, statistically, ethanol has the second most reliable results for used masses, with only one fairly minor anomaly. This may indicate that the curve is drawn to accommodate the three more deviant fuel enthalpies rather than those that should lie nearer the curve. * Similarly point B represents Propanol, which did not have a single used mass figure deviating + or -25% from the average, yet it deviates largely from the best fit curve. This is proof that the curve is in fact incorrectly drawn, as it fails to account for the anomalies of the results table (Figure 1). * What can be conceived as a more viable curve (taking into account the anomalies of Figure 1) is drawn on the same axes and labelled Z. INVESTIGATION: In reference to the question I was asked to answer, I believe that both my procedures, as well as my research and evaluative methods have proven what I aimed to, and also provided me with information to benefit future similar investigations. I have been able to prove and disprove my various predictions and state with more precision the actual impact of various factors on my final results. Therefore I can evaluate my effort as well-informed and productive in finding a viable conclusion based on statistical and chemical evidence. ...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. ## Experiment to determine the ethanol content of wine

5 star(s)

attempts of each part of the experiment are very close to one another, suggesting a high degree of accuracy each time it was repeated. To ensure this accuracy, the most accurate equipment available was used when measuring out volumes of liquids, such as using burettes instead of measuring cylinders.

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

Mass of spirit burner + lid + fuel after (g) Temperature of water before (0C) Temperature of water after (0C) Ethanol Trial 1 212.50 210.44 16 36 Ethanol Trial 2 210.41 208.44 17 37 I used 150 ml of water.

1. ## The Relationship Between The Number of Carbon Atoms In An Alcohol And Its Standard ...

Addition of: H There is an increase of: | C 2 C = O 1486 KJ | 2 O --- H + 926 KJ H Total energy Output: 2412 KJ ?This includes the addition of: 1 O = O 496 KJ 1/2 O = O 248 KJ 2 C ---

2. ## the analysis of aspirin tablet

Here are some possible reasons. Acetic acid and salicylic acid in the resulting solution may neutralize some of the sodium hydroxide in the solution. This may make the result greater. Some ingredients in the aspirin tablet are microcrystalline cellulose, croscamellose sodium, titanium dioxide, hydroxyl-methylcellulose, talc, iron oxide, polyvinyl acetate phthalate.

1. ## Investigation of Some of the Properties of a Pair of Cis-Trans Isomers

This is because the cis-butenedioic acid has a greater dipole moment than trans-butenedioic acid. 9. To improve heating effect during the determination of the melting points, the extensive arm of the tube was heated.

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

on the carbon atom this in turn means that the hydrogen atom and carbon atom become partially positively charged. The movement of electrons due to the electronegativity of one or more atoms creates a partial charge or .This is known as a dipole.

1. ## Classifications of Alcohols Experiment

observed, yellow colour remains 2-butanol Solution turns from yellow to greenish colour after heating n-butanol Solution turns from yellow to pale greenish colour after heating Alcohol X Solution turns from yellow to pale greenish colour after heating 1. Esterification test Reactants reagents Observations Ethanol Concentrated sulphuric acid (H2SO4)

2. ## Experiment Hypothesis: The energy released by an alcohol increases as the number of carbon ...

9. The process was repeated four different times with different alcohols ranging from methanol to Hexane. Then the energy change is calculated. DATA COLLECTION. Alcohol Initial mass of alcohol + spirit burner (g) ± 0.01 (M1) Final mass of alcohol +spirit burner (g)

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