is concerned with the shapes of molecules and how the differences in shapes can effect the properties and reactions of compounds. Subtle differences in molecular shape have far – reaching consequences and it is probably the field of molecular biology that a full awareness of molecular shapes has emerged. A knowledge of the molecular shapes of such vital compounds as sugars‚ amino acids‚ and proteins is essential in understanding their reactions and properties. Molecular structures are so frequently
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This molecular orbital model can be used to explain why He2 molecules don’t exist. Combining a pair of helium atoms with 1s2 electron configurations would produce a molecule with a pair of electrons in both the bonding and the * antibonding molecular orbitals. The total energy of an He2 molecule would be essentially the same as the energy of a pair of isolated helium atoms‚ and there would be nothing to hold the helium atoms together to form a molecule. The fact that an He2 molecule is neither
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number. The ions of two compounds exchange partners. AX + BY AY + BX This reaction can occur between two inorganic salts when one product is insoluble in water‚ driving the reaction forward. A typical example is as followed and is considered a molecular equation. BaCl2(aq) + 2AgNO3(aq) Ba(NO3)2(aq)+2AgCl(s) To better identify the strong electrolytes we write a more realistic equation as follows: Ba2+(aq)+2Cl-(aq)+2Ag+(aq)+2NO3(aq) Ba2+(aq)+2NO3-(aq)+2AgCl(s) This is called an ionic
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Name: __________________________________ ( ) Class: 4Q HWA CHONG INSTITUTION PRELIMINARY EXAMINATION 2010 CHEMISTRY 5072 Paper 1 Time: 1 hour INSTRUCTIONS TO CANDIDATES Do not turn the pages over until you are told to do so. Write your name and index number on the answer sheet in the spaces provided. There are forty questions on this paper. Attempt all questions. For each question‚ there are four possible answers labelled A‚ B‚ C and D. Choose the one you consider correct and
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long-chain backbone molecule with attached side groups. The preparation of polyurethanes is a process of polymerisation whereby a diisocyanate and a dihydroxyl compound react together. Polyurethanes by definition are linear polymers that have a molecular backbone containing carbamate groups (-NHCO2). These groups‚ called urethane‚ are produced through a direct chemical reaction between functional groups of a diisocyanate and a Polyol. First developed in late 1930s‚ polyurethanes are some of the most
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Hydrogen bond • Ionic attraction • Dipole-dipole forces • Van der Waals’ forces Computerized Molecular Modelling • Molecular modelling greatly speeded up the process of designing new medicines by eliminating the needs of conventional methods (trial and error). • By using molecular modelling‚ only molecules that fit with the active sites’ of the target are made and undergo clinical test. • Molecular modelling also used to design many other compounds like pesticides and polymers with specific
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1.1 CHEMISTRY 2213a ORGANIC CHEMISTRY FOR THE LIFE SCIENCES - organic chemistry is the study of life at the molecular level; to many it is the key to understanding life “The language of chemistry- an international language‚ a language without dialects‚ a language for all of time‚ and a language that explains where we came from‚ what we are‚ and where the physical world will allow us to go” (Nobelist Arthur Kornberg‚ a biochemist‚ 2000) - but its study has been challenging for students for
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concentration of solution is given by: ΔT = Kf m = Kf x mass of material__________ Molecular Weight x kg solvent Where‚ ΔT = freezing point depression Kf = freezing point molar constant of solvent m = molality concentration = mass of material / molecular weight x kg solvent = number of moles of solute / kg solvent METHODS Part 1 : Determination of the Freezing Point of Naphthalene
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6. POLYMERS and elastomers Lecture no. 1 Objectives: Definition‚ Functionality‚ Classification of high polymers – based on origin‚ molecular structure. 6.1.1. DEFINITION: The word polymer is derived from the two greek words‚ poly and meros‚ meaning many and parts or units respectively. Polymers are macro molecules formed by linking smaller molecules repeatedly‚ called monomers. Examples: Polythene is formed by linking a large number of ethene (or ethylene) molecules together
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Current‚ Voltage and Power * Electricity is the flow of electric charge. We can describe the flow of electric charge in several ways. These include the quantities Current‚ Voltage and Power. Current * Current (I) is the rate of flow of Charge Carriers‚ such as electrons. Current is usually thought of as moving in the direction of positive charge‚ so from the positive power supply to the negative. However‚ since in metals it is electrons that carry electric charge‚ the actually flow is opposite
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