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AS and A Level: Organic Chemistry
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Five equations you must know for organic chemistry
- 1 Alcohol + carboxylic acid = ester + water (eg CH3OH + CH3CH2COOH becomes CH3OOCH2CH3 + H2O)
- 2 Alkene + hydrogen = alkane (eg CH2=CH2 + H2 becomes CH3CH3)
- 3 Alkene + water = alcohol (eg CH2=CH2 + H2O becomes CH3CH2OH)
- 4 Halogenoalkane + hydroxide ion = alcohol + halide ion (eg CH3Br + OH- becomes CH3OH + Br-)
- 5 Alkene + hydrogen bromide = halogenoalkane (eg CH2=CH2 + HBr becomes CH3CH2Br)
Five facts about alcohols
- 1 Primary alcohols are oxidised into aldehydes and water, which are then oxidised into carboxylic acids. Secondary alcohols are oxidised into ketones and water. Tertiary alcohols cannot be oxidised.
- 2 Alcohols are oxidised by acidified potassium dichromate (H+/K2Cr2O7). This starts off orange and will turn green if it oxidises something (so with tertiary alcohols it will stay orange).
- 3 There are two ways of making alcohols: fermentation and hydration of alkenes. Fermentation is good because it uses renewable resources and does not take much energy, however it can only produce alcohol up to 14% before the yeast die.
- 4 Alcohols are soluble in water as they can make hydrogen bonds with the water. However, the “carbon chain” attached to the OH cannot interact with water and is insoluble. This means that alcohols become more insoluble the longer the carbon chain.
- 5 Alcohols have a very high melting and boiling point compared to alkanes of the same chain length. This is because they can form strong hydrogen bonds with each other that require a lot of energy to break.
Five facts about hydrocarbons
- 1 The longer the carbon chain the higher the higher the boiling point, as there will be more points of contact and stronger van der Waals forces.
- 2 The more branched the carbon chain the lower the boiling point, as the molecules will not be able to pack as close together and will have weaker van der Waals forces.
- 3 Hydrocarbons are insoluble in water as they cannot make intermolecular forces with them.
- 4 Hydrocarbons have low boiling and melting points as the only intermolecular forces that can hold them together are weak van der Waals forces which require little energy to break.
- 5 When processing crude oil (a hydrocarbon), the aim of the game is to get short, highly branched hydrocarbons. This will increase their volatility and make them a better fuel. We do this through: fractional distillation (sorts them into different sizes), cracking (splits long chains into short chains), isomerisation and reforming (makes the chains branched and cyclic).
In order to calculate the enthalpy change of Calcium Carbonate to Calcium Oxide, which is exceedingly hard to control and measure the energy change we must use Hess' law
With the enthalpy energy values for Calcium Carbonate and Calcium Oxide only then can we calculate the enthalpy change for Calcium Carbonate and Calcium Oxide. Enthalpy Calculations There are a few equations I must use to obtain my final answer firstly I must calculate the energy transferred in the reaction using the following equation:- Equation 1 Mass of liquid(g) x specific heat capacity of aqueous solution(Jg K ) x temperature rise(�C) = Energy Transferred (J) OR ?H = -M x Cp x ?T But this doesn't calculate the energy transferred per mole, to do this I must use:- Equation 2 = No.
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To Investigate Whether There is a Link Between the Number of Carbon Atoms in Alcohol and its Standard Enthalpy of Combustion
The energy is given out when forming the bonds between the new water and the carbon dioxide molecules. Here are the balanced equations for the alcohols that I will be using: Methanol - CH3OH + 11/2O2 ? CO2 + 2H2O Ethanol - C2H5OH + 3O2 ? 2CO2 + 3H2O Propanol - C3H7OH + 41/2O2 ?3 CO2 + 4H2O Butanol - C4H9OH + 6O2 ? 4CO2 + 5H2O Pentanol - C5H11OH + 71/2O2 ? 5CO2 + 6H2O Hexanol - C6H13OH + 9O2 ? 6CO2 + 7H2O Heptanol - C7H15OH + 101/2O2 ? 7CO2 + 8H2O Octanol - C8H17OH + 12O2 ?
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The three elements that will be used for this investigation are chlorine, bromine and iodine. Chlorine is a greenish yellow gas, which combines directly with nearly all elements. Chlorine is a respiratory irritant. The gas irritates the mucous membranes and the liquid burns the skin. Bromine is the only liquid nonmetallic element. It is a member of the halogen group. It is a heavy, volatile, mobile, dangerous reddish-brown liquid. The red vapour has a strong disagreeable odour, resembling chlorine, and is irritating effect to the eyes and throat. It has a bleaching action. When spilled on the skin it produces painful sores.
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The first four of the alcohols listed above have carbon chains with 1,2,3 and 4 Carbons. I chose to use these alcohols with an increasing number of carbon atoms in their carbon chains. The reason for this is I can investigate whether the change in the enthalpy of combustion increases by the same amount for every extra carbon in the carbon chain. I also decided to use octanol it has a carbon chain length of eight so it has twice as many carbons as butanol.
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For this experiment I have been given a task to determine which is the best Alcohol from its Homologous series. I can determine this by finding the Enthalpy change of Combustion for Alcohols.
Secondly, the temperature of the water also needs to be kept the same as well as the distance between the Crucible and the Sprit Burner. If the factors are not controlled then it will lead to the experiment being bias. The process in which I intend to avoid this from occurring is by controlling the temperature of the water using a thermometer and controlling the distance between the Crucible and Sprit Burner by measuring the distance using a 30cm ruler stick.
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Once my results have been obtained I will compare them against the theoretical enthalpy values. If they don't match up I will suggest some factors which conclude why. Hypothesis My hypothesis is that the more carbon atoms, the more heat will be produced. Alcohols produce heat when they burn in oxygen or air. Full combustion should generate only two products: CO2 and H2O. I predict that the alcohol with the greatest relative molecular mass will be the most efficient. Therefore, it will be Butan-1-ol as it has the greatest mass-per-mole of each of the four alcohols.
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The aim of this experiment was to recrystallise an impure sample of benzoic acid from hot water, and determine its purity through infra-red spectroscopy.
The beaker was then washed out with water several times and the remains were poured into the Buchner funnel. The glass rod was also rinsed and the remains were also transferred into the Buchner funnel. The crystals were then washed with cold water and left to dry for approximately 5 minutes. 6. A clean watch glass was then weighed and recorded using the four decimal point mass balance. As much of the crystals as possible were collected from the filter and transferred into the watch glass. The crystals and watch glass were then weighed and recorded together using a four decimal point mass balance.
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When denaturing occurs the original structure of the protein is lost and cannot reform. The enzyme becomes ineffective as a catalyst and reduces the rate of reaction as the concentration of enzyme is lowered. Each type on enzyme has its own range of pH in which it functions to its optimum. For example intercellular enzymes have an optimum pH of 7 that is neutral conditions. Strongly acidic or alkaline conditions denature enzymes. Intracellular enzymes such as digestive enzymes work best in acidic or alkaline conditions.
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The methanol catalyses the reaction, and splits the vegetable oil into 3 methyl esters. The glycerol which joined the 3 fatty acids is left over as a by-product. Candidate Vegetable Oils One of the main forms of energy is chemical potential that refers to the energy held within the bonds of chemical compounds present as both ionic and covalent bonds. Vegetable oils have a large amount of stored chemical potential energy. This is because the long acid chains have a large molecular weight, resulting in reserves of chemical energy within the bonds.
- Word count: 1403