Rates of reactions of halogenoalkanes

AS: ASSESSED PRACTICAL CHEMISTRY (Skill P) Rates of reactions of halogenoalkanes The relative rates of the reaction are observed by adding silver nitrate to the reaction mixture and timing the first appearance of the silver halide precipitate. This is the equation of hydrolysis of halogenoalkanes by aqueous silver nitrate. The X represents the halogen, e.g.; I, Br, Cl or halide I- , Br-, and Cl- The reaction below will be the same for all halogens. You just need to replace the halogen or halide, with any of the above. CH3 CH2 X + OH- CH3 CH2 OH + X- Ag+(aq) + X- (aq) AgX Nucleophilic Substitution of a halogenoalkane: *the bromine halogen can be replaced with any other halogen Prediction: I predict that the reactivity of the halogenoalkanes with AgNO3 is; *R = represents an alkyl group Most Reactive Least Reactive R-I > R-Br > R-Cl So I predict that alkyl iodide will have the fastest rate of reaction than alkyl bromide than alkyl chloride being the slowest. The amount of precipitate formed will show the rate of hydrolysis, and so I would expect to see iodobutane form the precipitate the fastest, and chlorobutane the slowest. Theory / Explanation: Nucleophilic substitution occurs in the hydrolysis of halogenoalkanes in a one step mechanism. Nucleophilic substitution happens when a molecule is attacked

  • Word count: 960
  • Level: AS and A Level
  • Subject: Science
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The Chemistry oh Phosphorous

The Chemistry of Phosphorus Among the non-metals, on the right hand side of the periodic table, with Atomic Number 15, is the element Phosphorus. The word 'phosphorus' is derived from the Greek word 'phosphoros' meaning 'bringer of light' and its discovery was completely accidental. It has the electronic configuration 2,8,5 and has 5 electrons in its outer most shell, hence it being in group 5 of the periodic table, under Nitrogen. In 1669, German alchemist Hennig Brand was attempting to create the 'philosopher's stone', which was a supposedly magical substance that would turn metals into gold, by evaporating urine. One day, after boiling urine into a paste, heating the paste to a high temperature and passing the vapours through water, where he hoped to find gold, was a mysterious white waxy substance that seemed to glow in the dark, and burst into flames when in contact with air. Brand had discovered phosphorus, well was the first to record this discovery. In fact, several other chemists could have discovered it at a similar time, and we now know that the substance he found was actually ammonium sodium hydrogen phosphate: (NH4)NaHPO41. This method produced only about 60g of phosphorus and used 1100L of urine, so was not very efficient, and it was only later on that investigators found alternative methods of obtaining it. One of its current processes of production

  • Word count: 2294
  • Level: AS and A Level
  • Subject: Science
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Demonstrate an understanding of the theory, principles and practice of separation of liquid mixtures by distillation techniques

Faculty: Technology Assign/Activity Code: 306/01 Course Title: C&G 0603 - Process Technology Instructions for the use of this cover sheet (1) A cover sheet is required for every activity including presentations (2) Please complete all sections below (3) Staple the cover sheet to your activity Student name: Billy Whelton Unit(s): LEVEL 3 Unit 306: Distillation in the Process Industry Assignment/ Activity title: 01 - Distillation techniques Hand out date: 5-10-2007 Hand in date: 0-12-2007 Graded (Y/N) N Resubmission date for referred work: 7-12-07 Student's comment on activity (if applicable): Student's Signature: ................................................ Date: ................. Assessment Grading Decision (by Assessor). Assessment decision following Verification. Activity designed by Assessed & graded by Key Skills Assessed by Name: Geoff Martin Name: Date: 28-06-05 Date: Internally Moderated by Internally Verified by Name: Name: Date: Date: You must store all marked activities in a portfolio (folder) for External Verification during the academic year. Grading descriptors PASS You have successfully completed all tasks and submitted all evidence as stated. Task Comments Pass Criteria Met Yes/No ALL All areas covered to a good level showing evidence of research and understanding YES Grading Comments Overall

  • Word count: 1440
  • Level: AS and A Level
  • Subject: Science
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Green Chemistry - greenhouse gases and the ozone layer

The 'Greenhouse effect' ? The greenhouse effect keeps us warm ? But, the enhanced greenhouse effect is responsible for global warming. Infrared radiation comes into the atmosphere and gets absorbed by the C=O, O-H and C-H bonds in H2O, CH4 and CO2. They vibrate gaining EK, which is dispersed, warming the Earth's surface. The greenhouse effect of a given gas is dependent on the: ? Concentration in the atmosphere (High CO2 etc) ? The ability to absorb infrared radiation (i.e. the bonding in it) The IPCC (bunch of chemists) collects evidence to force governments to stop producing so much CO2. Scientists should research ways in which global warming can be reduced ? Carbon-Capture and Storage (CCS)- This involves converting CO2 into liquid form. This liquid can be injected deep underground. ? Also reaction with metal oxides to form carbonates. (Magnesium Oxide) MO(s) + CO2(g) --> MCO3(s) ? The Kyoto Protocol was signed by developed nations governments to reduce output of greenhouse gasses to offset the progress of global warming. The scheme involved using carbon credits which can be traded around to penalise polluting nations. Some nations (Australia, USA (Obama)) are reluctant to join because of the impact on their economies.(See Geog notes) The ozone layer The Ozone Layer absorbs much of the harmful ultraviolet radiation emitted by

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  • Word count: 928
  • Level: AS and A Level
  • Subject: Science
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Obtaining pH curves for acid/alkali titrations.

Obtaining pH curves for acid/alkali titrations Obtaining pH curves for acid/alkali titrations Planning In order to obtain a pH curve, I must first devise a way in which to measure both the pH and the volume of alkali being added to the weak acid in order to draw a graph from my results and then from this graph find Ka. Method I will set up the equipment as shown in the diagram below: I will use a pipette and pipette filer to take 25cm3 exactly of the weak acid (0.1M ethanoic acid, CH3COOH) and place it in a beaker. I will then take a burette and place in it 50cm3 of 0.1M sodium hydroxide (NaOH). I will then measure the exact amount of NaOH added to the acid whilst using an accurate pH meter rather than indicator to measure the change in pH. Before using the pH meter, I will first dip it into two buffer solutions of pH 4 and pH 7 and calibrate it so that it reads accurately. I will record the values for the pH and the volume of NaOH added. Theoretically, this should give me a pH curve from which to work. In order to obtain a value for Ka, I shall find the equivalence point (at around 25cm3 where the graph goes up vertically) and find the pH at this point, I shall then divide this by two to give me the 1/2 equivalence point. Having obtained this value, I can assume that: [CH3COOH] = [CH3COO-] = [H3+O] And as: Ka = [CH3COO-] [H3+O] [CH3COOH] Therefore: Ka = [H3+O]

  • Word count: 1050
  • Level: AS and A Level
  • Subject: Science
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the partition coef of ethanoic acid between water and 2-methylpropan-1-ol

Determination of the distribution coef. of ethanoic acid between water and 2-methylpropan-1-ol Aim To determine the distribution (partition) coefficient for the equilibrium that exists when ethanoic acid is distributed between water and 2-methylpropan-1-ol. Principle By shaking ethanoic acid solution with 2-methylpropan-1-ol, the concentration of ethanoic acid in each solvent is determined by titration. The partition coefficient, Kd, can be obtained due to different solubility of solute in 2 solvents. Apparatus titration apparatus, separating funnel, 10ml pipettes, beakers, measuring cylinders Procedure . 15cm3 of the given aqueous ethanoic acid and 25cm3 of 2-methylpropan-1-ol were poured into a 100cm3 separating funnel, using suitable apparatus. The funnel was stoppered and was shook vigorously for 1 to 2 minutes. (The pressure in the funnel was released by occasionally opening the tap.) 2. 10cm3 of each layer was separated approximately. (The fraction near the junction of the two layers was discarded.) 3. 10.0cm3 of the aqueous layer was pipetted into a conical flask and was titrated with 0.1 M sodium hydroxide solution using phenolphthalein. 4. Using another pipette, 10.0 cm3 of the alcohol layer was delivered into a conical flask and was titrated with 0.1 M sodium hydroxide solution. 5. Steps (1) to (4) was repeated with another separating funnel using the

  • Word count: 894
  • Level: AS and A Level
  • Subject: Science
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Quantitative Determination of Food Colouring in Jelly Crystals using UV/Vis spectroscopy

Quantitative Determination of Food Colouring in Jelly Crystals using UV/Vis spectroscopy Aim : To study specific food colouring agents that shows a specific colour . To study the principles of absorbance spectroscopy. To tabulate and analyse data from an Excel spreadsheet. Introduction Food colouring are mainly used in the food processing industry today as colour gives the food product certain flavours as people associate colours with certain flavours. Some is to stimulate a colour that is perceived by the consumer as natural food products. Food colouring also provides an identity to foods, to mask natural variations in colour, decorative or artistic purposes or to protect flavours and vitamins from being damaged by light. Electron transition occurs when valence electrons in a molecule are excited from one energy level to a higher energy level (Silberberg,2008). The energy change associated with this transition provides information about molecular properties such as colour. Ultraviolet-visible spectrophotometry or UV-Vis refers to absorption spectroscopy in the UV visible spectral region. The absorption in the visible range affects the perceived colour of chemicals used in food products involved. In this region of the electromagnetic spectrum, molecules undergo electronic transitions from the ground state to the excited state The Beer-Lambert law states that the

  • Word count: 1417
  • Level: AS and A Level
  • Subject: Science
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Experiment to obtain curves which show how the pH changes during an acid-base titration and;To use these curves to choose suitable indicators for different combinations of acid and alkali.

Experiment 15 23-3-99 Aim: * To obtain curves which show how the pH changes during an acid-base titration and; * To use these curves to choose suitable indicators for different combinations of acid and alkali. Procedure: . 25.0cm3 of 0.100 M ethanoic acid was pipetted into a 100cm3 beaker, a small stirring paddle was added, and the beaker was stood on a magnetic stirrer. 2. The electrode of a pH meter was carefully clamped so that the bulb is completely immersed in the acid and is clear of the stirring paddle. If a magnetic stirrer (or mechanical stirrer) is not available, it is better to swirl the beaker by hand. If a pH meter is not available, it is better to use a conical flask rather than a beaker. 3. A burette with 0.100M ammonia solution was filled and was clamped over the beaker (or flask) containing the acid. 4. A value of the pH of the acid was obtained, either by reading the pH meter (which must, of course, have been calibrated) or by removing 1 small drop on a thin glass rod and testing with narrow range indicator paper. If which range to use was not known, it is first tested with full range universal indicator paper. However, it is important not to remove more than the minimum acid from the flask. 5. The alkali form the burette were added in steps as shown in result table and the pH at each addition was recorded after thorough mixing. 6. Steps 1~5 were

  • Word count: 1310
  • Level: AS and A Level
  • Subject: Science
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Additivity of Heats of Reaction: Hesss Law Design and Data Collection

IB Chem 11 Laura Hu Partner: Rhona Yue Worked together with Zheting and Melissa Additivity of Heats of Reaction: Hess's Law Purpose: To confirm Additivity of Heats of Reaction: Hess's Law. Supplies: As in text. Procedure: As in text. Reactions: Reaction #1: NaOH(s) + H2O(l) Na+ + OH- + q1 q1 is the difference in Heat for reaction 1 in Joules NaOH(s) is about 2.0g, and H2O(l) is 100mL Reaction #2: 100mL of 0.50M HCl(l) + about 2.0g NaOH(s) NaCl + H2O + q2 q2 is the difference in Heat for reaction 2 in Joules Reaction #3: 50.0mL 1.0M HCl(l) + 50.0mL 1.0M NaOH(l) NaCl + H2O + q3 q3 is the difference in Heat for reaction 3 in Joules Data Collection Table #3: Results collected by Rhona and Laura Initial Volume Mass of NaOH [m] Initial Final Temperature [t2] Reaction Temperature [t1] measured ± 0.005 (g) ± 0.2 (°C) ± 0.2 (°C) 00 ± 0.5mL of 2.93 21 22 H2O 2 00 ± 0.5mL of 2.87 20.9 26.5 0.50M HCl 50.0 ± 0.5mL 3 of 1.0M HCl ; N/A 20.4 26.7 50.0 ± 0.5mL of 1.0M NaOH Observation Notes: *Since these data is collected by us (Laura and Rhona), we have some observation notes about reaction 1, 2 and 3. Reaction 1: Temperature change is really slow. Reaction 2: Temperature raises a lot, but not very fast. Reaction 3: Temperature increases very fast. It jumped all the way to 26°C in 3 seconds right after pouring 50.0mL of 1.0M NaOH

  • Word count: 1093
  • Level: AS and A Level
  • Subject: Science
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Investigation into the chemist Fritz Haber

Coursework.info =) Research Project Chemist of choice: Fritz Haber Fritz Haber was born in the town of Breslau, Germany in early December 1868. His family was one of the oldest families in town, he was the son of Siegfried Haber who was a well know merchant in the town. Fritz studied at St. Elizabeth classical school in the town of his birth where he conducted many chemical experiments from a young age. From 1886 to 1891 Fritz studied chemistry at the University of Heidelberg under the academic advice of Robert Bunsen who had invented the Bunsen burner and also had help discover the elements cesium and rubidium. He also studied at the University of Berlin from guidance from A.W Hoffmann, and at the Technical School at Charlottenburg under Carl Liebbermann. Once he completed his studies at the universities he went and worked voluntarily for his father's chemical business as he was interested in chemical technology. He then went on to work at the under the eye off Professor Georg Lunge at the Institute of Technology in Zurich. After all this work he finally decided that he wanted to take up a scientific career and went to work with Ludwig Knorr at Hena for one and a half years to publish with him a joint paper on diacetosuccinic ester yet orthodox methods at the institute under Jena gave Haber little satisfaction. Still uncertain whether to devote himself to chemistry or

  • Word count: 925
  • Level: AS and A Level
  • Subject: Science
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