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Investigate and compare the amount of energy released during the combustion of alcohols with practical and theoretical combustions.

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Introduction

Chemistry Coursework Objective My aim is to investigate and compare the amount of energy released during the combustion of alcohols with practical and theoretical combustions. Combustion (burning) is the reaction of substance with oxygen. I aimed to use four different alcohols, these being: * Ethanol * Butanol * Proponol * Methanol Method I set up the apparatus as the diagram shows: To start the experiment I weighed the empty burner using electronic scales, and then added 75ml of the alcohol I was using, and then weighed it again. I then calculated the mass of alcohol in the burner. I then took the temperature of the water, and then lit the burner. I decided to keep the experiment running each time until the water had risen 200c. when this had happened I blew out the burner, and re-weighed it, so that I could calculate how much alcohol had been burned. At this point I used the formula: Energy = Mass of Water x Temperature Rise x Specific heat Capacity (g) ...read more.

Middle

+ (496 x6) (743 x8) (463 x10) O-C x1 360 ---------- ---------- ------------ O-H x1 463 2976 5944 4630 ------------ 5575 8551 10574 8551-10574 = -2023 Practical Start Temperature End Temperature Start Mass End Mass Mass Used 23 75 182.09 177.86 4.23 50g x 520 x 4.2 191035.461 ------------------- x 74 = --------------- = 191.035461 4.23 1000 Proponol C3H7OH + 4.5O2 3CO2 + 4H2O H H H O=O C=O H-O-H | | | O=O || H-O-H H - C - C - C - C - O - H + O=O C + H-O-H | | | O=O || H-O-H H H H (O=O%2) C=O || C || C=O || C Theoretical H - C x7 (412 x 7) O=O x (4.5) C=O x6 H - O x8 C - C x2 (348 x2) + (496 x 4.5 (743 x6) + (463 x8) O - C x2 360 --------------- ---------- ------------- O - H x1 463 2232 4458 3704 ---------------- 4403 6635 8162 6635 - 8162 = -1527 Practical Start Temperature End Temperature Start Mass End Mass Mass Used 25 45 184.9 184.0 0.9 21 41 ...read more.

Conclusion

The energy lost during the combustion has a)turned to water or steam and evaporated into the air. For example with Ethanol, when this is burned in air or oxygen the products are carbon dioxide and water. The water will evaporate into the air - this is where some of the energy goes as well as b)being taken up by breaking of bonds during the burning of the substance. When bonds are formed energy is released. If bonds that hold particles are to be broken or changed then energy has to be supplied to enable this to happen. The change is the difference between the energy liberated to form the bonds and that required to break the bonds. The experiment also proves that Exothermic process is followed because energy is liberated during the reaction proven by the end masses of the substances being lighter than the start masses. The quantities of energy produced depends upon the quantity of the chemical burnt as shown by the results. I.e. the higher the level of mass burnt or combusted the higher the level of energy released. ?? ?? ?? ?? Page: 1 ...read more.

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