Write an essay on electrode potentials.
F7 Essay Writing (Electrode Potentials) Q. Write an essay on electrode potentials. Outlines: (I) What are electrode potentials? (a) associated with equilibria of redox systems (half cells): e.g. metal / metal ion system ; non-metal / ion system ; ion / ion system; (b) reactivity, tendency for reduction to occur (losing electrons) and potential difference; (c) the potential difference of a half cell cannot be measured alone, but a relative value could be measured with another reference half cell / reference electrode; (d) a standard hydrogen electrode [SHE] (in which the emf is defined as zero) is used as the reference electrode; (II) How are electrode potentials measured? (a) concentration, temperature and pressure affect the emf of SHE, and the standard electrode potentials are obtained under conditions of 298K, 1 atm and conc. of 1M. (b) set up a cell with SHE and a salt bridge of electrolyte (e.g. KNO3); (c) a potentiometer is used to measure the cell emf (maximum potential difference), and the sign of cell emf = polarity of the right hand electrode. (III) How are electrode potentials used? / Application of electrode potentials? (a) calculation of cell emf ; (b) prediction of reaction feasibility and limitations. ~ Sample Essay ~ An electrode potential is the difference in an potential between an electrode and its surrounding electrolyte. It is
Revision Notes. Substances Manufactured for use in Industries. Chemicals, alloys and polymers.
.1 Manufacture of Sulphuric Acid Uses of Sulphuric Acid Sulphuric Acid, H2SO4, has many uses in our daily life. A few examples are: (a) Manufacture of fertilisers such as ammonium sulphate, (NH4) 2SO4 (b) Manufacture of electrolyte in lead-acid accumulators (c) Manufacture of soaps and detergents (d) Manufacture of pesticides (insecticide) (e) Manufacture of plastic items such as rayon and nylon (f) Manufacture of paints Manufacture of Sulphuric Acid in industry . Sulphuric acid, H2SO4, is manufactured in industry through the Contact Process. 2. The manufacturing of sulphuric acid, H2SO4, in industry involves three stages. Stage Aim Stage 1 Sulphur dioxide, SO2, gas can be produced by burning sulphur in air. S + O2 SO2 To produce sulphur dioxide, SO2, gas Stage 2 The gas mixture of sulphur dioxide and oxygen is passed over vanadium(V) oxide, V2O5 (catalyst) at a temperature of 450-500 ºC and under pressure of 1 atmosphere. 2SO2 + O2 2SO3 To produce sulphur trioxide, SO3 gas Stage 3 Sulphur trioxide, SO3, gas is dissolved in concentrated sulphuric acid, H2SO4 to form oleum, H2S2O7. SO3 + H2SO4 H2S2O7 Water is then added to the oleum, H2S2O7 to dilute it to produce sulphuric acid, H2SO4. H2S2O7 + H2O 2H2SO4 To produce sulphuric acid, H2SO4 The three stages involved in the Contact process Environmental
Experiment investigating hydrogen bonding in different chemicals.
Tsuen Wan Public Ho Chuen Yiu Memorial College Form 6 Chemistry Practical Experiment 8: Hydrogen Bonding Date of experiment: 27-1-2011 Objective: A. To discover the existence of hydrogen bonds between ethanol molecules B. To measure the strength of hydrogen bond formed between ethanol molecules C. To investigate the formation of hydrogen bonds between molecules of ethyl ethanoate and trichloromethane D. To measure the strength of hydrogen bonds formed between molecules of ethyl ethanoate and trichloromethane Introduction: A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond. These bonds can occur between molecules, or within different parts of a single molecule. The hydrogen bond (5 to 30 kJ/mol) is stronger than a van der Waals interaction, but weaker than covalent or ionic bonds. This type of bond occurs in both inorganic molecules such as water and organic molecules such as DNA. Intermolecular hydrogen bonding is responsible for the high boiling point of water (100 °C) compared to the other group 16 hydrides that have no hydrogen bonds. Intramolecular hydrogen bonding is partly responsible for the secondary, tertiary, and quaternary structures
Chiral Drugs What is chirality? Chirality is the property possessed by a molecule with such spatial arrangement of atoms that it cannot superimpose on its mirror image.
Chiral Drugs What is chirality? "Chirality" is the property possessed by a molecule with such spatial arrangement of atoms that it cannot superimpose on its mirror image. The object and mirror- image pair of molecules has the same constituents and structural formula. Their relationship with each other is similar to our left and right hands. The carbon atom of a simple chiral centre has four different groups arranged tetrahedrally (Fig. 1). Isomers of such nature are called enantiomers. Fig.1: A chiral molecule with tetrahedral arrangement and its mirror image. There are three types of stereoisomers, namely enantiomers, diastereomers and geometrical isomers. . Enantiomers are two stereoisomers containing asymmetric carbon atoms related as non-superimposable object and mirror images. If an enantiomer rotates polarized light to the right or in a clockwise direction, it is said to be the (+) or the dextrorotatory isomer. On the other hand, if the plane polarized light is rotated to the left or in a counter-clockwise direction, the isomer is called as the (-) or the levorotatory isomer. Enantiomers are identical in chemical and physical properties except for the direction of rotation of plane polarized light. 2. Diastereomers are stereoisomers that are not related as object and mirror images. They contain at least two asymmetric carbon atoms. Unlike enantiomers, the
Electrochemical Cells
Electrochemical Cells Tam Paul-Worika Contents Aim of the Investigation.....................................................3 Background.....................................................................3 * Redox Reactions * Electrochemical Cells * Salt Bridge * Nernst Equation Plan.................................................................................5 * Equipment * Risk Assessment * Instructions * Making the solutions Analysis...........................................................................7 Evaluation......................................................................17 Aim of the Investigation In my investigation, I will observe how changing the concentration of a solution can affect the electrode potential in an electrochemical cell. I will also see if there is a trend when the concentration is changed. Background Redox Reactions Redox reactions are reactions where the oxidation states of the atoms change[1]. The atoms are either oxidised or reduced, depending on if they lose or gain electrons. Electrochemical Cells Electrochemical cells (also known as Galvanic cells or Voltaic cells[2]), are devices that cause a current from chemical reactions. These reactions occur through redox. An electrochemical cell is set up so that the electrons lost from one of the reagents can travel to another reagent. This creates a voltage, which
Stereochemistry of Butenedioic acid
Name: Tonny, Chan Kar Yu, Student ID: 10297729 Date of Experiment: 19th February 2005, Group: B1 Title: Stereochemistry of Butenedioic acid Objective: To study the interconversion of two geometric isomers, maleic acid (cis isomer) to fumaric acid (trans isomers), the differences in physical properties between this pair of cis-trans isomers and determine the stereochemistry of addition of bromine to butenedioic acid. Chemicals and Apparatus: 2 grams of maleic acid, 10 cm3 of concentrated hydrochloric acid, 10 cm3 of bromine water1, one 50 cm3 beaker, one 100 cm3 beaker, one 250 cm3 beaker, one 10 cm3 measuring cylinder, one piece of spatula, one piece of water glass, one glass rod, a few pieces of filter paper, a set of Buchner funnel, a filter flask with side tube, three glass capillary tubes, a set of melting point apparatus, one long hollow glass tubing, one electronic balance, one heater and the oven Background: Stereochemistry is always encountered throughout organic chemistry. And stereochemistry isomerism can be divided into two classes, geometrical isomerism and optical isomerism. Although these categories are not mutually exclusive, it is not uncommon to find compounds that exhibit only one or the other of the two types. Most geometrical isomers result from cyclic systems or restricted rotation about double bonds. The preparation of fumaric acid by
Objective To find out the equilibrium constant, Kc, for the reaction below, using acid hydrolysis:
Determining an Equilibrium Constant Objective To find out the equilibrium constant, Kc, for the reaction below, using acid hydrolysis: Principle Although the hydrolysis of ethyl ethanoate is very slow, by using dilute hydrochloric acid as catalyst, the above equilibrium can be attained in 48 hours. After 48 hours, the reaction mixture can then be titrated with standard sodium hydroxide solution. Finally, the equilibrium concentrations of four components below and hence, Kc of hydrolysis of CH3COOCH2CH3 can then be calculated: Chemicals 2M HCl, 1.0335M NaOH, ethyl ethanoate, phenolphthalein indicator Apparatus 5 small reagent bottles, 5ml pipette & filler, burette, measuring cylinder, conical flask, electronic balance, stand, white tile Procedure -- Preparation, allow reaching equilibrium position 1.> Label 5 reagent bottles & their stoppers as 1A, 1B, 2, 3 and 4. 2.> Weigh each reagent bottles with their stoppers and record their corresponding masses in Table 3. 3.> Pipette 2M HCl into each bottles, using measuring cylinders to transfer ethyl ethanoate into bottles 2,3,4 and water into bottles 3,4 according to the amount shown in Table 1. Table 1 shows the amount of chemicals added: Reagent bottle's number A B 2 3 4 Volume of HCl(aq) added /cm3 5.0 5.0 5.0 5.0 5.0 Volume of CH3COOCH2CH3(l) added /cm3 - - 5.0 4.0 2.0 Volume of H2O(l) added /cm3
Write an account of buffer solutions.
F7 Essay Writing (Buffer Solution) Q. Write an account of buffer solutions. Guidelines: In your answer you should consider, giving examples, (a) definition (b) their compositions --- weak acid and its salt (acidic buffer), e.g. CH3COOH / CH3COONa --- weak base and its salt (basic buffer), e.g. NH3 / NH4Cl (c) how they work --- equilibrium shift after addition of a small amount of strong acid / strong base to buffer, --- resistance to pH change upon addition of small amount of acid / base (d) their applications --- for checking indicator solution and calibrating pH meters --- for controlling solution pH for chemical / biochemical reactions, --- for preserving food (e) their importance in nature --- maintenance of blood pH __________________________________________________________________________ ~ Sample Essay ~ A buffer solution is one which resists changes in pH when small amounts of acid or alkali is added to it. It plays an important role in chemical processes where it is essential that a fairly constant pH is maintained. Buffer solutions could be classified into two types, namely acidic buffer and basic buffer solutions. Acidic buffer solutions An acidic buffer solution is one which has a pH less than 7. They are commonly made from a weak acid and its sodium salt. A mixture of ethanoic acid and sodium ethanoate solutions is a typical example.
Heat of Neutralization. Objective: To investigate the enthalpy changes () of various acid-base neutralizations.
Title: Heat of Neutralization Objective: To investigate the enthalpy changes () of various acid-base neutralizations. Chemicals and Apparatus: .0M hydrochloric acid, ~1.0M sodium hydroxide solution, one thermometer, one polystyrene foam cup with lid, two pieces of 50.00 burette, two filter funnels, one piece of 25.00 pipette, pipette filler and a 100 beaker. Background: All chemical reactions involve energy changes. The study of energy changes is an important part of chemistry. Fundamental to the thermo-chemistry is the law of conservation of energy, which states that energy is neither created nor destroyed, but can be converted from one form to another. An exothermic reaction is one in which stored chemical energy is converted to heat energy (heat is released to the surroundings), conversely an endothermic reaction is one in which heat energy is converted to chemical energy (heat is absorbed into the system). The enthalpy (H) of a substance, sometimes called its heat content, is an indication of its total energy content. The equation for calculating the enthalpy change (heat change) is given by ?H = -m x c x ?T where m is the mass of the sample, c is the specific heat capacity of the sample and ?T is the change in temperature. The sign for ?H indicates the direction of heat flow, positive for endothermic processes and negative for exothermic processes. In this
Ozone chemistry speech. Today, I am here to inform you that an ozone hole has been detected over Antarctica and the concentration of ozone will continue to decrease across the globe if the emission of ODCs, such as CFCs, does not reduce.
ERT ORAL SCRIPT (Year 2004- Channel 7 news, slide 1) Breaking news in LA today is that the new movie premier The Day After Tomorrow is actually based on a true event that happened in 1986 at an international conference on climate change. However, it was not global warming leading into an ice age that was discussed, but (slide 2) the discovery of the ozone hole that biologically dangerous ultraviolet (UV) radiation cannot be completely absorbed to preserve the life forms on Earth. Thankfully, unlike the movie, 24 countries agreed to abide to the Montreal Protocol on substances that deplete the ozone layer, which aimed to gradually phase out all ozone-destroying chemicals, ODCs for short. Although measures have been taken, the ozone layer will not recover until the middle of this century as most ODCs have a lifetime of 20 to 100 years. Here coming up, is an extract from a video of the conference. (Year 1986, slide 3) Ladies and gentlemen, I am Professor Rowland. Today, I am here to inform you that an ozone hole has been detected over Antarctica and the concentration of ozone will continue to decrease across the globe if the emission of ODCs, such as CFCs, does not reduce. USA: The CFCs' industry is worth 8 billion dollars per year. I understand. The chemical is ideal for many purposes as it is used as a solvent and cleaning agent in the electronic industry, a non-toxic
