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GCSE: Organic Chemistry
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7. Replace water with cool water after the beaker has returned to room temperature 8. Repeat the stage for the same alcohol. 9. Repeat method for the other alcohols. How was it made a fair test? To make this a fair test I had to keep all the variables the same when using all alcohols The variables I needed to keep the same were: - ? Volume of water because if I didn't then it will take more energy to heat the larger volumes than it would the smaller volumes. I decided to use 200ml of water because I thought if I used any more it would take up a lot more energy from the alcohol and would have taken a long time for the experiment to be repeated.
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Water Clamp stand and clamp Tin can Thermometer Draught screens (optional) Heatproof mat Card above water Measuring cylinder Safety To prevent any injury we have to wear safety glasses and make sure all bags are out of the way. Diagram Variables Keep the same Change � Mass of the water 100cm � Same set of scales � Weigh the spirit burner with the lid on. � The height of the beaker from the wick � The type of alcohol used � Same tin can � Temperature rise of 25�C.
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I will work out the heat of combustion as shown below. The example I have worked out is butanol. The bond values are taken from the structure equation, Once the values for both the reactants and the products we calculate the heat of combustion by taking away the energy out from the amount of energy in. Butanol heat of combustion workings out I will work out the heat of combustion as shown below. The example I have worked out is butanol. The bond values are taken from the structure equation, Once the values for both the reactants and the products we calculate the heat of combustion by taking away the energy out from the amount of energy in.
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x O - H 1 x 460 = 460 3 x O=O 3 x 496 = 1488 + 4708kj 4 x C=O 4 x 740 = 2960 6 x O-H 6 x 460 = 2760 + 5720kj 4708 - 5720 = -1012kj Propanol - C3H7OH C3H7OH + 4 1/2 O2 3CO2 + 4H2O 2 x C - C 2 x 350 = 700 7 x C - H 7 x 410 = 2870 1 x C - O 1 x 360 = 360 1 x O - H 1 x 460 = 460 4 1/2 x O=O 4 1/2 x
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The heat energy released can be worked out from an equation. The equation is heat energy = vol of liquid x heat capacity (4.2) x temp change. Once this has been worked out you can find out the kJ/mol released if you have the mass. From the mass burnt you can find the number of moles burnt by doing mass/RMM of the alcohol. When you have the number of moles you divide the kJ released by this number and you get the kJ/mol released.
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If There Is a Relationship Between the Number of Carbon Atoms In Several Different Alcohols and the Heat of Combustion of Those Alcohols.
Repeat steps 2 - 6 twice more. 8. Repeat steps 2 - 7 for each of the other alcohols. Variables and Constants My variable will be:- number of carbon atoms present in the alcohol being tested. My constants will be:- increase in temperature. volume of water to be heated. Preliminary Experiment We were shown a preliminary experiment which we then used to develop our own methods. In the preliminary experiment a burner of hexane was weighed then placed under a can containing 100ml of water. The water was heated by 10�c then the burner was weighed again. This provided the basis for my method.
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This is the process where long chained alkanes are heated using a catalyst and due to this heat they break. The carbons then interconnect with other carbons to form mostly branched alkanes but sometimes two smaller chained alkanes. If this wasn't possible then the petrol would have a lower octane number and cause the engine to knock. Isomerisation : Petrol is formed when crude oil is seperated into its different components during fractional distillation. The crude oil is heated and sent into a distillation column.
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OH + 9O2 � 6CO2 + 8H2O = 2 moles of Propanol Structure of Reactants: 2x 9x H H H H - C - C - C - O - H O = O H H H = H - C x 14 (435) C - O x 2 (358) O - H x 2 (464) O = O x 9 (497) C - C x 4 (347) = 13595kj Structure of Products: 6x 8x O = C = O H - O - H = C = O x 12 (803)
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When I heating the measuring cylinder, I have to make sure the retort stand hold the measuring cylinder exactitude. Spirit burners are the safest way of burning the alcohol but we should not be to fill them. Scientific knowledge Stress the important of fair testing, for example the height of the flask above the wick. We can work out the number of moles used and find the energy produced per mole. A temperature sensor attached to a computer can be used in place of a thermometer. It can plot temperature change on a graph and allow better quantification of the heat produced.
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Method I have decided that I will: 1. Weigh the spirit burner with it's lid on first. 2. Measure 200cm3 of water and pour that into the calorimeter. 200cm3 is a good volume of water to start off with. Much less than this and the water would heat up to quickly, causing it to evaporate (which requires energy), thus losing energy. Much more than 200cm3, and the calorimeter would overflow. Therefore 200cm3 is a sensible volume. 3. Clamp the calorimeter 5cm above the spirit burner. 4. Note the initial temperature of the water.
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3. Prediction Because Butanol has the most bonds, I believe it must use the most energy. Bond Energy (Kj/mol) C - H 413 O - H 464 C - O 358 O - O 498.3 C - O 805 C - C 347 H - H 436 Using the bond energy values (shown above) I will try to work out how much energy the alcohols will give off. For example: CH3OH is the formula for methanol, and it contains 3 C-H bonds, 1 C-O bond and 1 O-H bond. Using the bond energy values from the above table I can work out how much energy is needed to break the bonds of CH3OH by adding all the values together.
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Results: Height of can from burner: 5cm Mass of burner at start = 204.47g. Mass of burner finish = 203.6g. Mass of fuel burned = 0.87g Start temp = 19oC Finish temp = 23oC, Temp rise = 4oC Following the pilot experiment I made some minor adjustments: Height of can above wick down to 4cm to improve contact with flame and stir the water, because the rise in temperature is too little. Apparatus * Glass Beaker * 100ml Water * Spirit Burner * Clamp Stand * 6 Fuels * Thermometer * Top-pan Balance * Ruler Method 1.
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1316 kJ > Ethanol Word Equation Ethanol + oxygen carbon dioxide + water Molecular Equation C (2) H (5) OH + 3O(2) 2CO(2)+ 3H(2) O Structural Equation H H | | H-C-C-O-H O=O H-O-H | | O=C=O H H + + H-O-H O=O O=C=O H-O-H O=O Bond Breaking Values Number Of Bonds to be Broken Type of Bond Relative amount of energy Needed per bond in kJ Total amount of energy needed in kJ 5 H-C 413 2065 1 C-O 358 358 1 C-C 347 347 1 O-H 464 464 3 O=O 498 1494 Total amount of energy needed to
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The crucible containing the fuel and the mineral wool will then be placed underneath the tripod and gauze. I will then use a ruler to check that the distance between the crucible and the gauze is 14cm. A tin can will be placed on top of the gauze, directly above the crucible, it will be filled with 100 cubic centimetres of water. I will then take the temperature of the water, before lighting the fuel in the crucible. I will wait until the fuel in the crucible has stopped burning and then I will take the temperature of the water again.
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Place the heat proof mat onto the side bench under the clamp claw 3) Weigh the sprit burner and record its weight. 4) Place the heat proof mat under-neither the clamp claw and then place the sprit burner on top of the heat proof mat 5) Get the copper container and place it into the clamp claw and tighten so it is suspended in mid-air. Then move the copper container and clamp claw so that the base of the copper container is 5cm away from the base of the showing wick.
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An endothermic reaction is the opposite of an exothermic reaction, it is one, which takes in energy from the surroundings, usually in the form of heat and is shown by a fall in temperature. Activation Energy or Eact represents the minimum energy needed by reacting particles for the reaction to occur. A catalyst, however, make reactions happen easier and quicker by reducing the initial energy needed, this is shown by the lower curve on the diagram below. The overall energy change for the reaction, Delta H ( H), remains the same though.
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The amount of energy that is theoretically released can be calculated when a fuel burns in sufficient oxygen to produce carbon dioxide and water as they are the only products of the reaction. Some of the energy that is released is kept and recycled to keep the fuel burning. The excess energy is given out in the form of heat. Which is called the heat of combustion. 1 mole of any substance always contains an identical number of particles. When calculating the heat of combustion we use the unit kJ/mole this allows you to compare the energy released by equal numbers of molecules.
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Ethanol is a colourless liquid with a burning taste and characteristic, agreeable odour. Ethanol is the alcohol in drinks like beer and wine. It is also used in thermometers below -38�C because mercury, which is also often used in thermometers, freezes at this point. Because of it's low freezing point it is used as an anti-freeze in car radiators. Ethanol is normally concentrated by distillation of dilute solutions. Ethanol melts at -114.1� C, boils at 78.5� C, and has a relative density of 0.789 at 20� C. Higher alcohols, those of greater molecular weight than ethanol, have many specific and general uses.
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Carbon monoxide is a poisonous gas. It combines with haemoglobin in the red blood cells and prevents it from carrying oxygen, hence reducing the capacity of the blood to carry oxygen 5.11 Recall that, in car engines, the temperature reached is high enough to allow nitrogen and oxygen from air to react, forming nitrogen oxides N2(g) + O2(g) ? 2NO(g) Nitrogen oxide is a major pollutant and greenhouse gas 5.12b Recall that sulphur dioxide and nitrogen oxides are pollutant gases which contribute to acid rain, and describe the problems caused by acid rain.
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These ions have difficulty in leaving the cell membranes. Instead, the ions accumulate and this damages the cell membranes. Damage of the cell membranes would cause bleeding. Even though a few milliliters of blood loss wouldn?t be harmful, excessive blood loss due to excessive use of aspirin could cause harm to the individual. 2.2 Properties of Aspirin They have low boiling points as compared to carboxylic acids even though they are polar molecules. This is due to the absence of intermolecular hydrogen bonding between ester molecules.
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5ml of concentrated 1mole/l of sulphuric acid was added turning the solution reddish brown. The solution was titrated with sodium thiosulphate solution until the solution turned pale yellow (during the addition of sodium thiosulphate solution the flask was shaken well to insure proper mixing of the solution). 2ml of starch solution was added turning the solution blue black and the titration continued until the solution go colourless or blue black colour disappear, the reading from burette were taken and the experiment was repeated until two concordant result or readings were achieved. The standardization of hydrated sodium thiosulphate also give the total amount of iodine present in the solution which is useful in the calculation of further experiment (as the concentration and volume of all the solution(potassium iodate,potassium iodide and sulphuric acid)
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