Variability and relative stability of oxidation states
Matt Carruthers Variability and relative stability of oxidation states In this essay the concentration will be on the oxidation states of the transition metals rather than the entire periodic table. An oxidation state is a number assigned to an element in a compound according to some rules. This number enables us to describe oxidation-reduction reactions, and balancing redox chemical reactions. Compared to Group II elements such as calcium, transition elements form ions with a wide variety of oxidation states. Calcium ions typically don't lose more than two electrons, whereas transition metals can lose up to nine. The energies required to remove electrons from calcium are low until you try to remove electrons from below its outer two s orbitals. In fact Ca3+ has an ionisation enthalpy so high that it rarely occurs naturally. However a transition element like vanadium has roughly linear increasing ionisation enthalpies throughout its s and d orbitals, due to the close energy difference between the 3d and 4s orbitals. Transition metal ions are therefore commonly found in very high states. Certain patterns can be seen to emerge across the period of transition elements: The number of oxidation states of each ion increases up to Mn, after which they start to drop. This drop is due to the stronger pull from the protons in the nucleus towards the electrons, making them
Method's of Drug Characterisation
Experiment 6 - Methods of Drug Characterization Aims . To gain experience of the analytical methods used for drug characterization Objectives . To gain experience in melting point determination, thin layer chromatography and UV spectroscopy 2. Application of the methods to identify an unknown substance Introduction The 2 most basic analytical techniques for identification of organic compounds are melting point determination and thin layer chromatography. Identification of compounds relied upon melting point determination before the modern analytical techniques of nuclear magnetic resonance, infrared and UV spectroscopy. Although thin layer chromatography still plays an important role in organic analysis. A solution of the unknown is spotted onto the silica coated plate about 1cm from the bottom and dried; it is then placed vertically into a tank with a suitable solvent inside. The solvent moves up the plate by capillary action and resolves the sample into discrete spots. The plate is removed and dried and the spots are viewed under UV or by treating it chemically with developing agent. For each component of the sample an Rf value can be calculated: Rf = distance moved by solute/distance moved by solvent Safety * Local rules apply * The sealing of melting point tubes by Bunsen must be done away from flammable solvents * After practical all waste solvents
Properties of Hydrocarbon
Title: Properties of Hydrocarbons Introduction: Hydrocarbons are organic compounds that contain only hydrogen and carbon. The simplest form of hydrocarbon is the methane, which have the structure of CH4. The hydrocarbons can be divided into two groups that are saturated and unsaturated hydrocarbon. The saturated hydrocarbons are the compounds in which all the bonds of the carbon contain single bond and all the carbons are filled with 4 bonds that are attached to other atoms. The single bond consists of a sigma bond. The saturated hydrocarbon is also known as alkane, which belongs to a homologous series of organic compounds in which the members differ by a constant relative molecular mass of 14. The chemical formula is Cn-H (2n+2), where n is the total number of carbons. The compound is said to be saturated when they follow Cn-H (2n+2), which is to say there are no double bonds. Unsaturated hydrocarbon, unlike saturated hydrocarbons, contain one or more carbon-carbon multiple bonds such as double bonds, triple bonds, or both. Instead of C – C, it contains C = C or C = C. These compounds rose due to the loss of two hydrogens because the carbons can only have four total bonds to it. Unsaturated carbons are also called alkenes or olefins with a general formula of Cn-H2n. In contrast to alkane, the bond consists of one sigma and one pi bond. Hydrocarbon can also be
Determination Of Nickel By Gravimetric Analysis
Title : Determination of Nickel by Gravimetric Analysis Objective : * To determine the amount of nickel in a given salt. * To calculate the weight percent of nickel in the salt and to compare with the Theoretical value * To study the gravimetric analysis method to determine the compound in a certain unknown salt Introduction and background Gravimetric analysis is a technique through which the amount of an analyte (the ion being analyzed) can be determined through the measurement of mass. Gravimetric analysis depend on comparing the masses of two compounds containing the analyte. The basic method of gravimetric analysis is fairly straightforward. A weighed sample is dissolved after which an excess of a precipitating agent is added. The precipitate which forms is filtered, dried or ignited and weighed. From the mass and known composition of the precipitate, the amount of the original ion can be determined. For successful determinations a few criteria must be met. First, the desired substance must be completely precipitated. In most determinations the precipitate is of such low solubility that losses from dissolution are negligible. An additional factor is the "common ion" effect, this further reduces the solubility of the precipitate. When Ag+ is precipitated out by addition of Cl- Ag+ + Cl- =<-> AgCl(s) the (low) solubility of AgCl is reduced still further by
Introduction to Molecular Modeling & Independent Molecular Modeling Project. Certain properties and characteristics of different molecules were observed via molecular modeling using the computer software PC Spartan Pro. Specifically, two molecules were se
Introduction to Molecular Modeling & Independent Molecular Modeling Project Discussion: Certain properties and characteristics of different molecules were observed via molecular modeling using the computer software PC Spartan Pro. Specifically, two molecules were selected as models: azomethine ylide and indole. In the azomethine ylide model, the electron density was observed while in the indole model, delocalization of bonds was taken into consideration. For the second model, azomethine ylide, single-point energy with Hartee-Fock 3-21G calculations using AM1 semi-empirical equilibrium geometry was also employed. Calculations were again based on the lowest-energy conformer of azomethine ylide, by the AM1 semi-empirical module. Figure 2 below presents the computer-generated model of azomethine ylide. Figure 1: PC Spartan Pro-Generated Structure of an Azomethine Ylide Figure 1 shows a general molecular structure of an azomethine ylide, a neutral molecule with a positive and a negative charge on adjacent atoms. As the program manual says, azomethine ylides are proposed intermediates of 1,3-dipolar cycloadditions. The ? system bears a formal negative charge which is neutralized by a formal positive charge in the ? system. Azomethine ylide was further studied by looking into the compound's electron density. Figure 2: Electron Density of Azomethine Ylide Figure 2 shows the
Innovative Methods of Hydrogen Storage for use as fossil fuel replacement.
INNOVATIVE METHODS OF HYDROGEN STORAGE FOR USE AS FOSSIL FUEL REPLACEMENT August 13, 2001 Fossil fuels have been the fuel sources of choice for modern civilization. There are limited stores of these fuels, and man must go to increasing lengths to extract available stores. This has had adverse effects on the environment, and environmentalists are increasingly successful in their efforts to preserve areas that contain these reserves of fossil fuels. The United States depends on oil for over 50% of its energy needs. The finite supply of this energy source is escalating the search for alternative energy sources. Also, the combustion products of these fuels contribute to air pollution and global warming, further threatening the quality of life for all. Nuclear power generation was once thought to be the power source of the future. However, accidents at nuclear power facilities and disposal problems with the products of energy generation using this method have resulted in the rethinking of this energy source. Electric vehicles have been touted as the next step to eliminate reliance on fossil fuels. The stumbling block on this path is efficient and lightweight storage of enough power to parallel fossil fuel vehicles already in use. To date, there has been no storage system that can produce enough power to economically and safely power a vehicle for realistic use.
ALDEHYDE AND KETONE
EXPERIMENT 3: ALDEHYDE AND KETONE OBJECTIVE To identify carbonyl compounds as aldehyde and ketone using qualitative analysis. INTRODUCTION O Carbonyl compounds have functional group called carbony C and there are two types of carbonyl compound that is aldehydes and ketones. Both aldehydes and ketones have general formula, CnH2nO O O General structure of aldehyde is R-C-H whereas ketone is R-C-R'. Aldehyedes are named by using the suffix-AL while for ketones, it was named by using the suffix-ONE. Carbonyl compounds can be prepared from the following reactions. . Oxidation of alcohol 2. Ozonolysis of alkene that involve the breaking of C=C carbon double bond. 3. Friedle-Craft Acylation ( aromatic ketone ) in the presence of ALCL3 as a catalyst. In Fehling's test, only aliphatic aldehydes ( not aromatic aldehyde, ketone) react with Fehling's reagent. In the reaction, aldehyedes is oxidized to form a carboxylate and copper (11) ion is reduced to copper (1) oxide which appear as brick-red precipitate. Both aliphatic and aromatic aldehyde (not ketone) react with Tollen's reagent. In the reaction, aldehyde is oxidized to form carboxylate and the Ag(NH3)2 positive ion which appear as silver mirror on the wall of the test tube. An aldehyde will react positively with schiff's reagent giving pinkish purple colour
Determination Of The Valency Of Magnesium
Title : Determination of the Valency of Magnesium Objective: . To determine the stoichiometry of the magnesium 2. To study the quantitative relations between amounts of reactants and products of the reaction. Theory & Background : Stoichiometry is the study of the combination of elements in chemical reactions. Stoichiometry refers to the relative number of atoms of various elements found in a chemical substance and is often useful in characterizing a chemical reaction. The related term stoichiometric is often used in thermodynamics to refer to the "perfect mixture" of a fuel and air. Stoichiometry is often used to balance chemical equations. In this experimet, a known starting mass of magnesium and the measured collection of hydrogen gas will be used to determine the reaction stoichiometry. Stoichiometry rests upon the law of conservation of mass, the law of definite proportions and the law of multiple proportions. In general, chemical reactions combine in definite ratios of chemicals. Since chemical reactions can neither create nor destroy matter, nor transmute one element into another, the amount of each element must be the same throughout the overall reaction. This experiment determines the stoichiometry of a reaction of magnesium and hydrochloric acid(HCl). The relationship between moles of magnesium reacted and moles of hydrogen produced are plotted.
A 0.60 um film of silicon dioxide is to be etched with a buffered oxide etchant of etch rate 750 A min-1. Process data shows that the thickness may vary up to 10% and the etch rate may vary up to 15%.
Andy Somody 97300-6222 ENSC 495 Assignment #3 6-1). a). A 0.60 um film of silicon dioxide is to be etched with a buffered oxide etchant of etch rate 750 A min-1. Process data shows that the thickness may vary up to 10% and the etch rate may vary up to 15%. The maximum possible thickness of the silicon dioxide film is therefore 110% of its nominal value. Therefore, the maximum possible thickness of the silicon dioxide film can be determined through the following calculation: where zmax is the maximum possible thickness of the silicon dioxide film and znominal is the nominal thickness of the silicon dioxide film. Therefore, znominal = 0.60 um. Any number expressed as a percentage can alternatively be expressed as a decimal. For example, 110% can be expressed as 1.1. Using this decimal format, the above formula can be rewritten in the following manner: Substituting our previously determined value for znominal into the above formula yields: with significant figures applied Similarly, the minimum possible etch rate of the buffered oxide etchant is 85% of its nominal value. Therefore, the minimum possible etch rate of the buffered oxide etchant can be determined through the following calculation: where rmin is the minimum possible etch rate of the buffered oxide etchant and rnominal is the minimum possible etch rate of the buffered oxide etchant. Therefore, rnominal =
Chemical Preservatives.
Title: Chemical Preservatives .Calcium disodium EDTA It was found in "mayonnaise". Properties It is the salt of ethylene diamine tetraacetic acid (EDTA). Utilization It is applied as a chelating agent. Its function is to control the reaction of metal ions with some organic and inorganic components that will result in deterioration of foods. Apart from that, the preservative also acts as antioxidant antimicrobial agent, especially against gram-negative bacteria. Mechanisms of action Ca disodium EDTA blocks the normal reaction of metal ions by binding to their reactive sites. This increases its efficiency as an antioxidant. Consequently, the oxidation of ascorbic acid and fat-soluble vitamins is hindered and also the rancidity of the product. The resistance of gram-negative bacteria is overcome by the removal of lipopolysaccharide containing membrane. 2.Calcium Propionate (C6H10CaO4) It was found in " wholemeal bread rolls". Properties It is the salt of propionic acid. It is only soluble in water but insoluble in alcohol. Utilization The antimicrobial activity is particularly against mycotoxin forming moulds, less so against bacteria. No inhibition effect has been demonstrated against yeast. Therefore, it is mainly used for bread preservation, as it will not interrupt the leavening in