chemistry OCR-open book 2008
Section1: Discuss with the use of examples the main difference between Alpha decay and Beta decay: An alpha particle consists of 2 protons and 2 neutrons (He- nucleus), which is emitted as the nucleus looses 2 protons and 2 neutrons to become more stable. In this process a new chemical element is produced and this process is called transmutation, and this is a spontaneous reaction. For example the decay of Uranium-238 into Thorium- 234 E.g. 1 Beta decay: A beta- particle is a high energy electron, emitted when a neutron in the nucleus decay to form a proton and an electron. E.g. 1 E.g. 2 The differences between alpha and beta decay: Alpha decay Beta decay It's a form a nuclear fission reaction, where the atom splits in to two daughter nuclei. An energetic negative electron is emitted, producing a daughter nucleus of one higher atomic number and the same mass number. Alpha decay is restricted to heavier elements; an element only emits an alpha particle is it atomic number is less than 82. Beta particle is emitted when a heavy element decays with atomic number of above 82 decays. Alpha radiation reduces the ratio of protons to neutrons in the parent nucleus. A beta particle is emitted when there is too many neutrons, a neutron decays into a proton, an electron and an antineutrino. Difference between nuclear fission reaction and
Rates of Halogenoalkanes
Rates of Reaction of Halogenoalkanes I have been asked to design an experiment to examine how the rate of reaction of halogenoalkanes varies with respect to the C-X bond. I will be varying the C-X bond using the halogens chlorine, bromine and iodine (C-Cl, C-Br or C-I) to see which of these bonds gives the fastest rate of hydrolysis. Other factors that affect the rate of reaction are temperature, concentration of reagents, pressure, surface area and the use of a catalyst, however I will make sure that these remain constant, in order to ensure that only the chosen variable (the halogenoalkanes) is causing any difference to the rate of hydrolysis. The hydrolysis of the halogenoalkanes involves a nucleophilic substitution reaction. The mechanism for the reaction is as follows. Firstly as the halogen atom is more electronegative than the carbon atom, the C-X bond is polarised to become, C?+ - X?- . The positive charge of the carbon atom promotes attack by a nucleophile (a chemical that donates a pair of electrons to form a new covalent bond) this causes heterolytic fission of the carbon-halogen bond to occur and the halogen atom is displaced as a halide ion. A new covalent bond is then formed between the nucleophile and the carbon. Suitable nucleophiles to substitute a halogenoalkane are the hydroxide ion, water and ammonia. Chemical Equations: Equation of hydrolysis reaction
Explosives experiment
Explosives. Oxidation Oxidation is the loss of electrons. Oxidation occurs when gunpowder explodes, it contains carbon, sulphur and potassium nitrate. The carbon and sulphur are both oxidised to form gases. The potassium nitrate carries oxygen, meaning it is an oxidising agent and gunpowder carries it's own oxygen supply for the reactions. This makes the explosion very powerful as the oxygen is available as soon as the gunpowder is ignited. C(s) + O2(g) --> CO2(g) The carbon gains oxygen and it's oxidation number increases from 0 to +4 making CO2. Oxidation means there is a faster reaction as there are oxygen molecules to react with. The more oxygen molecules the more violent the reaction. Development Gunpowder was the first explosive used, it was a good explosive as it contained it's own oxygen supply. It was made of carbon, sulphur and potassium nitrate (the oxidiser). However it produced large quantities of white smoke so wasn't effective as a weapon as it obscured the opposition. Cellulose nitrate was then produced by reacting cellulose with nitric acid and sulphuric acid. This did not produce smoke when it exploded so the visibility on battlefields was improved. A fuse wasn't needed as cellulose nitrate could be ignited by percussion, and larger quantities could be used. To use as an explosive cellulose trinitrate and nitro-glycerine were mixed together.
Chemistry paper outline: Nicotine I. History and facts A. Naming and group
Chemistry paper outline: Nicotine * I. History and facts * A. Naming and group * a. Solanaceae group of plants classified by it's nicotine which consists of plants such as potatoes, eggplants, tomatoe,etc. * b. most commonly associated with tobacco plants, found when biosynthesis happens * c. Named by the plant Nicotina tabacum * B. Key history * a. 1600's-1700's- Nicotine was introduced to Europe in tobacco and later brought to America, associated with god and later on evil. * b. 1800's-Scientists like Vauquelin and Poselt began studying Nicotine and discovered facts about it such as its weight, formula, structure, etc. * C.1900- Scientists began studying nicotine medical terms as how it can help and damage humans. * d. Many synthesis studies of nicotine occurred. * II. The chemistry of nicotine * A. Chemical and Physical Data * a. Density of 1.01 g/cm3 * b. Melting point of 110 F and a boiling point of Boiling point of 477 F * c. Described as a colorless poisonous gas occurring naturally in tobacco. * d. empirical formula of C10H14N2 and has a molar mass of 162.26 g/mol. Half life of about 2 hours and a bioavailability of 20-45% * B. Chemistry * a. Nicotine is soluble in water and non polar. * b. When in nitrogen form it produces salts with acids. * c. Although it boils, it can burn under the temperature of its boiling point. The vapor it produces
Identifying an unknown chemical
Compound A Compound (A) has no effect on blue litmus paper, and so it is not an acid. When reacted with 2,4-dinitrophenylhydrazine, an orange precipitate is formed. This indicates the presence of a C=O (carbonyl) bond. This suggests that (A) must be an aldehyde or a ketone. There is no reaction with sodium carbonate, so there is no O-H (alcohol) group the lack of observable reaction with sodium confirms this. Because there is no noticeable change when mixed with bromine water, there cannot be a C=C bond (an alkene would decolourise bromine water, forming a halogenoalkane). There is no change when heated with ethanoic acid and sulphuric acid, further indication that (A) is not an alcohol. According to the 2,4-dinitrophenylhydrazine (Brady's reagent) test, (A) must be an aldehyde or a ketone. To determine which of these it is, Tollen's reagent is used. When (A) is heated with Tollen's reagent (ammoniacal silver nitrate), no observable change occurs. This tells us that (A) must be a ketone- had (A) been an aldehyde, a "silver mirror" would have been formed on the test tube. This is because Tollen's reagent ( [Ag(NH3)2]+ ) is reduced upon heating with aldehydes, forming silver metal. From these data, I believe (A) to be a ketone. However, this must be confirmed by the use of the spectra. On the NMR spectrum, there is a single peak at 2.2 ppm. This has a relative peak area of 6.
Oxidation of ethanol
The oxidation of Ethanol Safety The Chemicals used in the experiment were: * Ethanol * Sodium Dichromate * Sulphuric Acid * Universal Indicator * 2, 4-dinitrophenylhydrazine The above chemicals did have some hazards when in the context of this experiment. Due to these hazards I wore a lab coat to protect from things like the Na2Cr2O7, which stains, also I wore protective glasses to prevent things from entering my eyes. Below are the hazards. Ethanol * Highly flammable above 13°C causing a narcotic effect if inhalation of the vapour occurs. * Toxic Sodium Dichromate * Very Toxic › Cause cancer if inhaled * Harmful if swallowed * Harmful if in contact with skin * Danger to environment - Very to toxic to aquatic environment may * Cause long-term adverse effects Sulphuric Acid * Very corrosive - cause severe burns * Dangerous with - Sodium, dangerous reactions can take place Water, Vigorous reactions when the concentrated acid is diluted Universal Indicator * Contains several ingredients which are flammable, so it must be kept away from flames. Observations During the course of the experiment I wrote down a few observations including smells, colours etc. Below are the observations for the experiment in the order of observing them. . At the very beginning when I added the concentrated sulphuric acid to the
To determine the enthalpy change of a reaction
To determine the enthalpy change of a reaction Analysis Results These are the results I obtained from reacting CaCo3 with Hcl and CaO with Hcl, these 2 experiments were done after one another. The temperature changes of each reaction will then be used to determine the enthalpy change. Reaction with CaCO3 CaO Mass used (g) 2.48 .41 Temperature of acid (Hcl) initially (ºc) 24 24 Temperature of solution after mixing (ºc) 26 36 Temperature change during the reaction (ºc) 2 2 Looking at these results it suggests that CaO was a more reactive reaction and a more exothermic reaction than CaCO3 as more energy was released than the reaction with CaCO3. However, we can see that both reactions were exothermic as when the reaction finished both temperatures of the solution after mixing the reactant with the Hcl rise. We can see that these reactions were not endothermic as the temperatures of the solution would have lowered as energy would have been absorbed. Calcium carbonate, CaCO3 decomposes with heat. CaCO3 (s) --> CaO(s) + CO2 (g) Calcium oxide reacted with Hydrochloric acid: CaO(s) + 2Hcl(aq) --> CaCl(aq) + H2O Both calcium oxide and calcium carbonate react readily with 2 mol dm-3 hydrochloric acid (Hcl). The temperature changes during the reactions, these reactions can be measured and the enthalpy change can be determined. ?H1 and ?H2 can be calculated. ?H
Ethanoic acid
Production of Ethanoic Acid Introduction I am doing this experiment to try and find out whether I can produce ethanoic acid in a college laboratory. Hopefully I will produce ethanoic acid and hopefully it will be pure. Also, I will be synthesizing the ethanoic acid. Equipment * Anti-bumping granules * Dilute sulphuric acid * Pear shaped flask * Potassium dichromate * Concentrated sulphuric acid * Bunsen burner * Gauze * Tripod * Clamp stand Method . Put a few anti-bumping granules and 10 cm3 of dilute sulfuric acid in the round bottomed flask. 2. In a fume cupboard, add in 5 g of potassium dichromate and dissolve by careful swirling. 3. Slowly with swirling and cooling in an ice bath, add 6 cm3 of concentrated sulfuric acid. 4. Mix 15cm3 of ethanol and 10 cm3 of deionised water in the dropping funnel. 5. Add the solution from the dropping funnel drop wise down the condenser, while swirling the contents of the flask and cooling it if necessary to prevent too vigorous a reaction. 6. Set up the apparatus for reflux distillation. 7. Boil the mixture gently using a water-bath for about half an hour. 8. Cool the apparatus dismantle and rearrange for distillation. 9. Distil off about 15 cm3. This is aqueous ethanoic acid. Purification The mixture is put into the round bottomed flask along with a few anti-bumping granules, and the
Synthesis of Aspirin
Aim In the first part of the experiment was to synthesize quality of aspirin (Acetylsalicylic acid) and in the second part of the lab, the TCL plate was performed to confirm the identity of the aspirin and to detect any impurities. Introduction Acetylsalicylic acid normally known as aspirin and often used to relieve pain, reduce inflammation, and lower fever. The first aspirin was synthesized in 1893 by Felix Hoffman and Arthur Eichengrün. There were about 325 milligrams of acetylsalicylic acid in average tablet. [i] The chemical name of aspirin was 2-acetoxybenzoic acid and the structural formula was: [iii] In this experiment aspirin (3) could be prepared by a slow reaction between salicylic acid (2) and ethanoic anhydride (also known as acetic anhydride) (1) with a small amount of catalyst, which in this experiment used sulphuric acid as the catalyst. [ii] The chemical equation was: (CH3CO)2O (l) + C6H4(OH)COOH (l) H+ CH3COOH (l) + C6H4(OCOCH3)COOH (l) [ii] Reagents needed during experiment: Salicylic acid Ethanoic anhydride (acetic anhydride) Concentrated sulphuric acid Distilled water Mixture of methanol: dichloromethane in the ratio of 1:8 by volume Ethanol Container of ice Equipment needed during experiment: ) For the 1st part of the lab: Gloves Scale Boiling tube Thermometer Test-tube holder Steam bath Fume cupboard 00cm3 conical flask Glass
Aim: To determine how the concentration of each species in a reaction affects the rate of reaction
Aim: To determine how the concentration of each species in a reaction affects the rate of reaction Plan Introduction In this coursework, the rate of reaction between two reactants will be investigated. Rate of reaction can be defined as the time during which a reactant is lost or a product forms during a chemical reaction. This is calculated by dividing the value of concentration by the time in seconds. There are factors other than concentration that affect the reaction rate, which are temperature, surface area and a catalyst. However, the effect of concentration is the only factor being investigated, meaning that the other factors need to remain constant, and in the absence of any catalyst. Theory Increasing the concentration of a solution increases the reaction rate. This is because there are more particles in the solution, making molecular collisions more likely. Therefore, more collisions between particles take place. The reaction that will be examined in order to fulfil the aim is the reaction between sodium thiosulphate solution and dilute hydrochloric acid: 2HCl(aq) + Na2S2O3(aq) 2NaCl(aq) + SO2(g) + S(s) + H2O(l) The experiment is carried out by constructing a large cross on a piece of paper, and placing this beneath the reaction mixture. Hydrochloric acid is then mixed together with sodium thiosulphate. The concentration of one of the reactants
