Enthalpy change of magnesium in combustion Rui Shen Chemistry 4U – Ms .Brazier 2/28/2013 Introduction: Hess ’s law is a terminology in chemistry named after Germain Hess‚ a Swiss-born Russian chemist and physician who published it in 1840. The law states that the total enthalpy change during the complete course of a reaction is the same whether the reaction is made in one step or in several steps. Enthalpy cannot be directly measured‚ but rather the change in enthalpy. Enthalpy is described
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within the substance. This stored chemical potential energy is the heat content or enthalpy of the substance. The collection of substances that is involved in a chemical reaction is referred to as a system and anything else around it is called the surroundings. If the enthalpy decreases during a chemical reaction‚ a corresponding amount of energy must be released to the surroundings. Conversely‚ if the enthalpy increases during a reaction‚ a corresponding amount of energy must be absorbed from
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TABLE OF CONTENTS 6.1 The Nature of Energy 6.2 Enthalpy and Calorimetry 6.3 Hess’s Law 6.4 Standard Enthalpies of FormaCon 6.5 Present Sources of Energy 6.6 New Energy Sources 30 STANDARD ENTHALPIES OF FORMATION Cgraphite(s) Cdiamond(s) ΔH for this process cannot be obtained by
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GRAAD 12 NATIONAL SENIOR CERTIFICATE GRADE 11 PHYSICAL SCIENCES: CHEMISTRY (P2) EXEMPLAR 2013 MARKS: 150 TIME: 3 hours This question paper consists of 13 pages‚ 1 data sheet and a periodic table. Copyright reserved Please turn over Physical Sciences/P2 2 NSC – Grade 11 Exemplar DBE/2013 INSTRUCTIONS AND INFORMATION 1. Write your name in the appropriate space on the ANSWER BOOK. 2. This question paper consists of TWELVE questions. Answer ALL the questions in the ANSWER BOOK. 3. You
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which depends only on state of system not upon path is called state function eg. P‚ V‚ T‚ E‚ H‚ S etc. 4. Extensive & Intensive Properties: Properties which depends on quantity of matter called extensive prop. eg. mass‚ volume‚ heat capacity‚ enthalpy‚ entropy etc. The properties which do not depends on matter present depends upon nature of substance called Intensive properties. eg. T‚P‚ density‚ refractive index‚ viscosity‚ bp‚ pH‚ mole fraction etc. 5. Internal energy: The total energy
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To begin the analysis‚ the properties of the air at the base of the tower were examined. The wet and dry bulb temperatures of the air at the inlet were used to find the humidity‚ humid volume‚ and enthalpy of dry air. For example‚ in the first trial the dry bulb temperature was 22.5⁰C and the wet bulb was 16.5⁰C‚ and the properties found from the psychrometric chart are listed below. H_bottom=0.0095 kg/(kg dry air) V_bottom=0.85 m^3/(kg dry air) h_bottom=47 kg/(kg dry air) Then‚ the cross-sectional
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The Dissolving of Solid Sodium Hydroxide in Water Procedure: 1. Measure out approximately 200 mL of distilled water and pour it into the calorimeter. Stir carefully with a thermometer until a constant temperature is reached. Record the volume of water and the constant initial temperature of the water on your data table. 2. Place a plastic measuring trough on top of the digital balance‚ and then zero the balance (press the tare button) so that the mass of the trough will be "ignored" and
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2013/07/09 Lecture Presentation Chapter 5 Thermochemistry John D. Bookstaver St. Charles Community College Cottleville‚ MO © 2012 Pearson Education‚ Inc. Energy • Energy is the ability to do work or transfer heat. – Energy used to cause an object that has mass to move is called work. – Energy used to cause the temperature of an object to rise is called heat. Thermochemistry © 2012 Pearson Education‚ Inc. 1 2013/07/09 Kinetic Energy Kinetic energy is energy an object possesses
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difficult to derive the exact enthalpy in a reaction when multiple processes occur simultaneously. A method to circumvent this problem is outlined in Hess’s Law which was established in 1840. Hess’s Law states that the steps taken to determine the enthalpy of a reaction do not matter because the end results will be the same. This is the principle used for both parts of this experiment. In Part I of the experiment‚ two different reactions are performed to determine the enthalpy of formation for magnesium
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24.31g/mol = 0.01275 moles no of moles of HCl = molarity x volume = 1.0M x (25/1000)mL = 0.025 moles heat of reaction will be 0.025 moles as HCL act as the limiting reactant. Enthalpy change of the reaction‚H2 Volume of HCL solution = 25 mL Assume the solution has the same density and specific heat capacity as water. Volume of HCL solution = 25 mL ρ = mass/volume 1.0g/cm³ = mass/ 25 cm³
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