Qualitative Analysis
Objective: To increase the power of observation and deduction, to give a practice at obtaining and interpreting IR spectra and to identify an unknown compound G. Introduction: Organic compound are so numerous and of such wide variety that the problem of identification is formidable unless approached in a systematic and logical manner. Both spectroscopic and chemical techniques are useful for solving these problems. The general procedures for the identification of an organic compound are: . Preliminary physical examination. 2. Determination of the solubility properties of the compound. 3. Qualitative element analysis- for element present in the compound other than carbon, hydrogen, and oxygen. 4. Chemical characterization tests- to determine the chemical class of the compound. 5. Spectroscopic analysis- to determine the chemical class of the compound and its structure by interpretation of the IR spectra. 6. Literature search- compares the physical and the spectroscopic properties of the unknown compound with compounds of the same chemical class. 7. Further experiment comparisons- to provide addition chemical tests data that are necessary to complete and confirm the identification. Methodology: First of all, the physical state, color, size and shape and odor of the unknown compound G were recorded. Secondly, ignition test and solubility test were carried out.
GCSE Chemistry - Alcohols Coursework
GCSE Chemistry - Alcohols Coursework Planning This investigation involves burning alcohol in the air. Key science- Chemistry by Eileen Ramsden says that " an alcohol is a series of organic, homologous compounds, with the general formula Cn H2n+1OH". The alcohol reacts with the oxygen in the air to form the products water and carbon dioxide: Cn H2n+1OH +(n+n/2)-1O2 ? nH2O + nCO2 The structure of the molecules in this reaction is: H H | | H - C - C - O- H + 3[O=O] ? 1/2[O=C=O] + 3[H-O-H] | | H H This reaction is exothermic, as heat is given out. This is because the amount reactant energy is more than the product energy the difference between this is ?H, therefore some energy has been given out in the form of heat.The energy is given out when forming the bonds between the new water and carbon dioxide molecules. This can be shown in an energy level diagram: Reaction co-ordinate ?H is the heat content, which is the enthalpy, which is negative in exothermic reactions as the diagram shows that energy is 'lost' as heat. Enthalpy is defined as the energy of reaction, or the heat energy associated with a chemical change. Chemical Principles By Master & Slowinski says that "For any reaction carried out directly at a constant pressure, the heat flow is exactly equal to the difference between enthalpy of products and that of the reactants", or: Qp = Hp - Hr = ?H Where Qp is the
Determining activation energy (Ea) of a reaction
Determining activation energy (Ea) of a reaction Objective To determine the activation energy for the reduction of peroxodisulphate(VI) ions. S2O82-, by iodide ions I-, using a 'clock' reaction. Principle The equation for reduction of S2O82- by I- is: S2O82- + 2I- › 2SO42- + I2 The formation of iodine is 'monitored' by small & known amount of thiosulphate ions, S2O32-: 2S2O32- + I2 › S4O62- + 2I- Once the reactants are mixed, the stop-watch is started. At the time when all of the thiosulphate is reacted, any free iodine produced will turn starch solution (added before) into dark-blue, the time is then recorded. The amount of thiosulphate added monitors the time in which starch turns blue and the reaction rate is directly proportional to 1 ÷ time taken for starch changes to dark blue. By plotting a graph of log10(1/t) against 1/T (T=absolute temperature), activation energy (Ea) can be found. Chemicals 0.020M K2S2O8, 0.50M KI, 0.010M Na2S2O3, 0.2% starch solution Apparatus 400 cm3 beaker, boiling tubes x2, pipettes (10ml), thermometer x2, water bath, stop-watch Procedure 1.> Half-fill the beaker with hot water at temperature between 49 - 51? (as water bath). 2.> Pipette 10 cm3 of 0.020M K2S2O8 solution into the first boiling tube, place a thermometer in this solution and keep this in the water bath. 3.> Pipette 5 cm3 of both 0.50M
IDENTIFICATION OF AN ORGANIC UNKNOWN
IDENTIFICATION OF AN ORGANIC UNKNOWN When doing each procedure, take extra care and wear eye protection, gloves, and lab coat because there's a high risk due to the organic chemical been unknown. Risk assessment before the test alkene and phenol: Procedure / Chemical Risk Precaution Information derived from Bromine water Toxic: very toxic by inhalation. Irritant: irritant to skins and eyes Harmful: by inhalation, contact with skin or swallowed. If swallowed, wash out mouth and drink a glass or two of water. Seek medical attention as soon as possible. If inhaled, remove victim and put where there's fresh air. If chemical gets into eyes, wash off with plenty of water and seek medical help. Wear eye protection and gloves during handling. Dispose using fume cupboard. Cleapss card page number 15 Unknown organic compound Explosive: risk of explosion by shock, friction, fire, or other source of ignition. Toxic: by inhalation or if swallowed. And it's very toxic to skin. Skin stain yellow on contact with which may be followed by dermatitis. If swallowed, wash out mouth and drink a glass or two of water. Seek medical attention as soon as possible. If inhaled, remove victim and put where there's fresh air. If chemical gets into eyes, wash off with plenty of water and seek medical help. Wear eye protection, and wear gloves during handling of chemical. If chemical
identification of an organic unknown
Identification of an Organic Unknown Aim: You are supplied with an unknown compound containing one of the following functional groups: - Alkene - primary alcohol - tertiary alcohol - aldehyde - ketone - carboxylic acid - ester - phenol Outline a sequence of tests to identify the unknown compound. Before carrying out the tests, I will label each test tube A-H so I can distinguish between different samples. Tests I will use: Sodium Metal Test Procedure: - Place 2cm depth of the organic compound in a test tube. - Remove the oil from a small piece of sodium - Add the sodium to a test tube containing the organic compound. - Bubbles of gas are a positive result. Safety¹: Sodium is flammable so make sure there are no naked flames near the sodium. Sodium reacts with water so do not wash out test tubes in the sink. Ensure test tubes are completely dry before use. Wear goggles to prevent sodium getting in eyes and do not handle the sodium as it may react with skin - especially if wet. Do not test the gas with a lighted splint because sodium is flammable! Bromine Test Place 1cm³ of the organic compound in a test tube and add bromine water (which is an orange-brown colour) drop by drop until no further change. Shake the mixture. If the compound is an alkene - the bromine water will go colourless. Safety: Bromine is toxic and corrosive so wear gloves
Identification of an organic unknown
Identification of an organic unknown Here is the flow chart to determine the unknown organic. Start with the 2,4-DNP test and then follow the chart. DNP - 2,4-dinitrophenylhydrazine test The Safety: • DNP is harmful - avoid contact with skin, eyes etc. Wear safety glasses. • At this stage we have no idea what the organic chemical to be tested is, so wear gloves. The Instructions: To 1cm3 of 2,4-dinitrophenylhydrazine (DNP) solution, add a few drops of the unknown organic substance. If a yellow/orange precipitate is formed, it indicates the presence of a carbonyl group (aldehyde or ketone) (positive result). Move on to the Tollen's reagent test. If no precipitate is formed (negative result), move on to the Bromine water test. The Chemistry: 2,4-dinitrophenylhydrazine bonds to carbonyl compounds and makes an orange precipitate. The reaction also releases water. Tollen's reagent test The Safety: • Silver nitrate is poisonous and harmful, particularly to the eyes and nose. It will stain skin. • Sodium hydroxide is an irritant when dilute. • Aldehydes and ketones may be toxic. • Silver metal poses little threat. • Ammonia in solution is particularly damaging to the eyes, besides being toxic if swallowed and harmful to the skin. • Wear goggles and gloves, avoid contact with chemicals. The Instructions: Tollen's reagent must be prepared within
Identification of an unknown Organic Compound
Identification of an unknown Organic Compound The organic compound that I have to identify can have several functional groups. These are: * Alkene * Phenol * Carboxylic acid * Aldehyde * Ketone * Primary alcohol * Tertiary alcohol * Ester The functional group in an alkene is that it has a double bond. This function allows an alkene to undergo addition reactions as it has an area of high electron density that attracts electrophiles. Therefore, in order to test for alkenes, I will use the Bromine water test as bromine can act as an electrophile. A bromine molecule may have instantaneous dipole between each other. This causes the + end of the dipoles to attack the high electron density area. If the unknown compound is an alkene, than the bromine water which is originally brown will decolourise. The mechanism for this reaction shown below; However, phenol will also decolourise bromine water as well as form white precipitant. This is an indication that the unknown compound is a phenol rather than an alkene. Phenol is an aromatic compound similar to Benzene but one of the hydrogen atoms is substituted by and OH group. Phenol molecules form hydrogen bonds resulting into white crystalline solid. When aqueous bromine reacts with a phenol molecule, the hydrogen atoms in the phenol are substituted by the bromine atoms. Thus the final product is 2,4,6-tribromophenol. The
Identifying an Unknown Compound
Identification of an Unknown Organic Compound Ensure a lab coat, safety glasses and gloves are worn during the experiments and work in a ventilated area. For all experiments test tubes and pipettes will be required. ALKENES: Alkenes contain a double carbon-carbon bond. APPARATUS: Unknown compound, bromine water. METHOD: Add 5 drops of bromine water to a test tube containing 1cm3 of the unknown and shake. OBSERVATION: Bromine water will decolourise from orange. EXPLANATION: The alkene decolourises bromine water and produces 1,2-dibromoethane. The double bond allows electrophilic addition reactions to occur. HAZARDS: Bromine vapour released from the water is 1^harmful^1 (see appendix). ESTERS: Esters are sweet- smelling products from reactions between carboxylic acids and alcohols. APPARATUS: Unknown compound, phenolphthalein, water bath, NaOH. METHOD: 1Add 5 drops of phenolphthalein and NaOH to the unknown in a test tube and shake. Then heat the solution in a water bath.1 OBSERVATION: A pink colour will appear once the indicator has been added and when heated the pink colour will disappear. EXPLANATION: This reaction is the hydrolysis of an ester; the pink colour disappears as the ester has completely reacted with NaOH and forms the salt of sodium. HAZARDS: Phenolphthalein- 2^irritant^2. NaOH- 1^harmful^1 and 3^corrosive^3. PHENOLS: Phenol has the formula
Combustion Of Alcohols.
Combustion Of Alcohols Planning This investigation involves burning alcohol in the air. Key science- Chemistry by Eileen Ramsden says that " an alcohol is a series of organic, homologous compounds, with the general formula Cn H2n+1OH". The alcohol reacts with the oxygen in the air to form the products water and carbon dioxide: Cn H2n+1OH +(n+n/2)-1O2 ? nH2O + nCO2 The structure of the molecules in this reaction is: H H | | H - C - C - O- H + 3[O=O] ? 1/2[O=C=O] + 3[H-O-H] | | H H This reaction is exothermic, as heat is given out. This is because the amount reactant energy is more than the product energy the difference between this is ?H, therefore some energy has been given out in the form of heat.The energy is given out when forming the bonds between the new water and carbon dioxide molecules. This can be shown in an energy level diagram: Reaction co-ordinate ?H is the heat content, which is the enthalpy, which is negative in exothermic reactions as the diagram shows that energy is 'lost' as heat. Enthalpy is defined as the energy of reaction, or the heat energy associated with a chemical change. Chemical Principles By Master & Slowinski says that "For any reaction carried out directly at a constant pressure, the heat flow is exactly equal to the difference between enthalpy of products and that of the reactants", or: Qp = Hp - Hr = ?H Where Qp is the heat flow at
Finding out how much acid there is in a solution
Plan: Finding out how much acid there is in a solution [Oliver White] Theory During the extraction of a metal from its ore, sulphur dioxide is often produced. This can be converted to sulphuric (IV) acid and sold as a useful by-product. With a given sample of the acid solution, with concentration thought to be between 0.05 and 0.15 mol dm-3, I am asked to accurately find its concentration. I am provided with solid anhydrous sodium carbonate and the indicators; methyl orange and phenolphthalein. Screened methyl orange is also available for people who are colour blind and have difficulties noticing colour changes when using the methyl orange. The choice for my experiment is only between methyl orange and phenolphthalein as I have no trouble using the methyl orange. To help choose which indicator would be most suitable we are given details about the solubility of indicators for different types of titration; Strong Acid Weak Acid Hydrochloric acid Ethanoic acid Nitric acid Ethanedioic acid Sulphuric acid Strong Alkali Weak Alkali Sodium hydroxide Ammonia solution Potassium hydroxide Sodium carbonate Calcium hydroxide Sodium hydrogencarbonate For a titration between a strong acid and a weak alkali, methyl orange is used as the indicator. For a titration between and weak acid and a strong alkali, phenolphthalein is used as the indicator. For a titration between a
