Redox Titration Aims/Objective : To determine the molar concentration of the given KMnO4 solution.
Chemistry TAS Report . Experiment Number : 16 2. Date : 30/04/2008 3. Title : Redox Titration 4. Aims/Objective : To determine the molar concentration of the given KMnO4 solution. 5. Introduction / Theory: 6. Relevant Equations/Chemical Reactions Involved : Half-equation : MnO4-(aq) + 8H+(aq) + 5e- › Mn2+(aq) + 4H2O(l) C2O42-(aq) › 2CO2(g) + 2e- Overall equation : 2MnO4-(aq) + 16H+(aq) + 5C2O42-(aq) › 2Mn2+(aq) + 8H2O(l) + 10CO2(g) 7. Chemicals : Oxalic dehydrate acid crystal 1.58 g KMnO4 solution 80 cm3 1 M dilute sulphuric acid 80 cm3 8. Apparatus and equipment : 250 cm3 conical flask 3 burette 250 cm3 beaker 2 filter funnel 25.0 cm3 pipette pipette filler safety spectacle white tile wash bottle 250 cm3 volumetric flask 00 cm3 beaker 2 dropper heat-proof mat Bunsen burner 25 cm3 measuring cylinder 9. Procedure : . 1.58 g of oxalic acid crystal was weighted accurately which was then dissolved in distilled water. 2. The solution was transferred to volumetric flask and made up to 250 cm3 (the mark) by distilled water. 3. 25 cm3 of oxalic acid was pipetted in a conical flask. About 25 cm3 of 1 M dilute sulphuric acid was added to it so that the solution was acidified. 4. The mixture was heated to about 60 oC by Bunsen burner. 5. The hot mixture was titrated with KMnO4 solution until the colour changed
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
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
Determination of the Enthalpy Change of a Reaction
Determination of the Enthalpy Change of a Reaction Determine the enthalpy change of the thermal decomposition of calcium carbonate by an indirect method based on Hess' law. Using the proposed method of obtaining results, these values were gathered: Reaction 1: CaCO3(s) + 2HCl(aq) ?Cl2(aq) + CO2(g) + H2O(l) Experiment Number Mass of CaCO3 (g) Temperature Change (?) 2.50 2 2 2.55 2 1/6 3 2.50 2 1/4 4 2.53 2 1/6 5 2.47 2 µ 2.51 2.12 Reaction 2: CaO(s) + 2HCl(aq) ?Cl2(aq) +H2O(l) Experiment Number Mass of CaO (g) Temperature Change (oK) .30 9 1/2 2 .36 0 1/3 3 .46 1 4 .35 0 1/6 5 .40 0 1/2 µ .37 0.3 µ in both cases represents the mean of the data. Using the equation for enthalpy change: ?H = mc?T Where: m = Mass of liquid to which heat is transferred to (g) c = Specific heat capacity of aqueous solution (taken as water = 4.18 J.g-1.K-1) ?T = Temperature change (oK) We can thus determine the enthalpy changes of reaction 1 and reaction 2 using the mean (µ) of the data obtained. Reaction 1: ?H = 50 x 4.18 x -2.12 ?H = -443.08 This value is for 2.51g of calcium carbonate, not 100.1g which is its molecular weight. Therefore: ?H = -443.08 x (100.1 / 2.51) = -17670.2 J.mol-1. ?H = -17.67 kJ.mol-1. Reaction 2: ?H = 50 x 4.18 x -10.3 ?H = -2152.7 This value is for 1.37g of calcium oxide, not 56.1g which is its relative molecular
Qualitative Analysis (A combined approach using spectroscopic and chemical analysis for structural identification of organic compound)
Student Name: Chan Yu Yan Maggie (Applied Biology) 22nd Nov, 2006 Student ID: 50920875 Group: B-2 BCH 2007 Principles of Organic Chemistry Experiment 8: Qualitative Analysis (A combined approach using spectroscopic and chemical analysis for structural identification of organic compound) Introduction In organic chemistry, the idenctification of organic compounds is a problem that is often encountered. As there are numerous of organic compounds of such wide variety in the world, identification is really difficult unless approached in a systematic and logical manner. To solve these problems, both spectroscopic and chemical techniques are useful. The general procedure for the identification of an organic compound consist of preliminary physical test, solubility test, qualitative elemental analysis, chemical characterization tests, spectroscopic analysis, literature search and further experimental comparisons. Objective: To identify the two unknown samples BL (molecular mass: 88.11 g, b.p.:76-78?C) and BS (molecular mass:122.17 g, m.p.:22-23?C) with known b.p or m.p and molecular mass by carry out different examinations, tests and spectroscopic analysis. Materials and Methods Procedure for preliminary physical examination The physical state, colour, shape and size, viscosity and odour of both the unknown solid and liquid were observed and recorded. For the
Determination of calcium and magnesium in water by EDTA
Determination of calcium and magnesium in water by EDTA Water hardness is a very important quality and is one of the most commonly determined water quality parameters. Metal ions present in water contribute to the hardness of water. Cations of Calcium and Magnesium are the main contributors, and to a lesser extent cations of barium and strontium. The Mg² and Ca² ions are therefore the measure of the hardness of water. These ions present in water are usually from water sources that originate from limestone or chalk geological formations. They often accompany the alkalinity ions: carbonate, bicarbonate and hydroxide. Thus the alkalinity of a water sample can be a reasonable guide to water hardness. Water hardness is an important quality used for municipal or industrial purposes. A certain degree is necessary in municipal water systems to prevent corrosion of pipes. Hard water causes curdy precipitate with soap, therefore reducing its ability to solubilize dirt. Ca² + H C-(CH ) -COO ›[H C-(CH ) -COO ] Ca² Although a small degree of water hardness is beneficial to health, it can be a problem for hot water boilers or heaters. The formation of Calcium Carbonate precipitates onto the heater coils and reduces its efficiency: (boiler scale) CO² + Ca² › CaCO In this experiment the hardness of an unknown water sample will be determined by titration
The theory behind enthalpy changes
The theory behind enthalpy changes Exothermic reactions are most common, however, an important example of an endothermic reaction is photosynthesis in plants, where the energy supplied is from sunlight. Law of conservation of energy: Energy cannot be destroyed or created but only transferred from one form to another. The total energy of a system of reacting chemicals and surroundings remains constant. Enthalpy change is the term used to describe the energy exchange that takes place with the surroundings at a constant pressure and is given the symbol DH. Enthalpy is the total energy content of the reacting materials. It is given the symbol, H. DH = DH products - DH reactants The units are kilojoules per mole (kJmol-1) An exothermic enthalpy change is always given a negative value, as energy is lost to the surroundings. DH = -xkJmol-1 An endothermic enthalpy change is always given a positive value, as the energy is gained by the system from the surroundings. DH = + ykJmol-1. Standard enthalpy changes: standard conditions If we are to compare the enthalpy changes of a various reactions we must use standard conditions, such as known temperatures, pressures, amounts and concentrations of reactants or products. The standard conditions are: A pressure of 100kilopascals (102kPa) A temperature of 298K (25oC) Reactants and products in physical states, normal for the
Investigation of the Order of the Reaction of Iodine with Propanone
F.6 Chemistry Experiment Date 7th March 2008 Experiment No. 5 Title Investigation of the Order of the Reaction of Iodine with Propanone Objective To investigate the order of the reaction of iodine with propanone. Introduction The rate of a chemical reaction is affected by the concentration of reactants according to the rate equation, which has to be determined experimentally. Iodine react with propanone as following: CH3COCH3(aq) + I2(aq) CH3COCH2I(aq) + HI(aq) By titrating the remained iodine in the reaction mixture against standard sodium thiosulphate solution at various times, the rate of reaction can be determined. By further varying the initial concentration of propanone while keeping the initial concentration of iodine constant, the relationship between rate of reaction and concentration of propanone can also be established. Experimental Procedure • 25.0 cm3 of sodium thiosulphate solution was diluted to 250 cm3 in a standard flask. • 25 cm3 of sulphuric acid, V1 cm3 of propanone solution and V2 cm3 of distilled water was measured using a measuring cylinder, and was then added into a conical flask as follows : Student pair A B C D Volume of propanone solution (V1) / cm3 25.0 20.0 5.0 0.0 Volume of distilled water (V2) / cm3 0.0 5.0 0.0 5.0 • 50 cm3 of iodine solution was added to the propanone
Enthalpy Experiment
Lauren Crawley 10 LE 6-March-2002 Enthalpy Experiment I will be trying to obtain reliable results which tell me the relationship between the number of carbon atoms, in particular alcohols: Methanol, Ethanol, Propan-1-ol and Butan-1-ol, and the amount of heat energy given out, known as the enthalpy of combustion. The combustion process is the making and breaking of bonds. In my experiment heat will be given out (it will be an exothermic reaction) In an exothermic reaction the products are at a lower energy level than the reactants, the difference is the heat energy. The complete combustion of an alcohol is when it reacts with oxygen in the air to form water and CO2. Fuel is a substance that is generally burned to produce thermal energy. Using these 4 alcohol fuels I aim to find out how much heat energy each alcohol produces. I am going to investigate this energy release by burning alcohol- "enthalpy of combustion" and how the number of carbon atoms in each of the alcohols affects the enthalpy change occuring during combustion. 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
Enzyme catalysed decomposition of hydrogen peroxide
Objective The purpose of my experiment is to determine the effect of different concentration of copper Hydrogen Peroxide on the activity of catalase and the production of oxygen. Background Knowledge Catalase is an enzyme which is globular protein - the secondary protein structure is folded into a spherical or globular shape. Hydrogen bonds, ionic bonds, disulphide bridges and hydrophobic interactions (between groups of amino acids) maintain the specific three dimensional shape of the enzyme. This specific 3D shape is very essential for the functioning of enzymes. The part of the enzyme which binds with the substrate is called the active site. The shape of the active site differs from one enzyme to another. This makes the enzyme react only with a specific substrate, which fits the active site. Enzymes also lower the activation energy and provide an alternate (lower energy) pathway for the reaction to proceed. Thus the rate of reaction speeds up (catalyst). Figure 1 The enzyme active site binds to hydrogen peroxide (substrate) and decomposes it to oxygen and water. Catalase (Yeast) Hydrogen Peroxide Water + Oxygen 2H2O2 2H2O + O2 Figure 2 There are many factors which affect the activity of enzymes; the concentration inhibitor is one of the factors which have a massive effect the activity of enzyme. An enzyme
