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Thermochemistry

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Thermochemistry

  1. 1. THERMOCHEMISTRY  Guided By: Presented By : Shivang Bansal  Mr. Rahul Gupta (0818CM141011)
  2. 2. CONTENTS :  Definition  History  Measurement  Certain laws to be followed while writing thermo chemical equations  Thermo chemistry in daily life  Importance of thermo chemistry
  3. 3. DEFINITION : •Branch of chemistry which deals with the quantity of heat evolved or absorbed during a chemical reaction. •In other words, study of energy or heat in chemical reaction and/or physical transformation. •It also helps in determining whether reaction is spontaneous or non- spontaneous. •It coalesces the concepts of thermodynamics with concept of energy in forms of chemical bonds Commonly includes calculations of -: 1. Heat capacity 2. Enthalpy 3. Entropy 4. Free energy 5. Calories 6. Heat of Combustion 7. Heat of formation
  4. 4. HISTORY : • Thermochemistry rests on two generalizations-: 1. Lavoisier and Laplace’s law (1780): The energy change in any transformation is equal and opposite to energy change in the reverse process. 2. Hess' law (1840): The energy change in any transformation is the same whether the process occurs in one step or many. These statement helps in formulation of first law of thermodynamics in 1845. In 1858, Gustav Kirchhoff gave the variation of the heat of reaction given by formula : dH/dT ΔCp Integration of this equation gives value of heat of reaction from one value of temperature to another value of temperature.
  5. 5. MEASUREMENT : Calorimeter-: 1. Is a enclosed chamber used for heat measurement in which change examine occurs. 2. Temperature is maintained using thermocouple and thermometer. 3. Temperature v/s time graph is plotted to calculate fundamentals units like heat change, heat of formation or combustion etc. First ice calorimeter used in winter (1782- 1783). Differential Scanning Calorimeter
  6. 6. CERTAIN LAWS TO BE FOLLOWED :  ΔH is directly proportional to the quantity of a substance that reacts or is produced by a reaction.  ΔH for a reaction is equal in magnitude but opposite in sign to ΔH for the reverse reaction.  ΔH is independent of the number of steps involved.This rule is called Hess's Law. It states that ΔH for a reaction is the same whether it occurs in one step or in a series of steps. Another way to look at it is to remember that ΔH is a state property, so it must be independent of the path of a reaction.  If Reaction (1) + Reaction (2) = Reaction (3), then ΔH3 = ΔH1 + ΔH2
  7. 7. THERMOCHEMISTRY IN DAILY LIFE:  All types of vehicles that we use, cars, motorcycles, trucks, ships, aeroplanes, and many other types work on the basis of second law of thermodynamics and Carnot Cycle. They may be using petrol engine or diesel engine, but the law remains the same.  All the refrigerators, deep freezers, industrial refrigeration systems, all types of air-conditioning systems,heat pumps, etc work on the basis of the second law of thermodynamics.  All types of air and gas compressors, blowers, fans, run on various thermodynamic cycles.
  8. 8.  One of the important fields of thermodynamics is heat transfer, which relates to transfer of heat between two media. There are three modes of heat transfer: conduction, convection and radiation. The concept of heat transfer is used in wide range of devices like heat exchangers, evaporators, condensers, radiators, coolers, heaters, etc.  Thermodynamics also involves study of various types of power plants like thermal power plants, nuclear power plants, hydroelectric power plants, power plants based on renewable energy sources like solar, wind,geothermal, tides, water waves etc,  Renewable energy is an important subject area of thermodynamics that involves studying the feasibility of using different types of renewable energy sources for domestic and commercial use.
  9. 9. IMPORTANCE OF THERMOCHEMISTRY  Thermochemistry is a very important field of study because it helps to determine if a particular reaction will occur and if it will release or absorb energy as it occurs.  It is also possible to calculate how much energy a reaction will release or absorb and this information can be used to determine if it is economically viable to use a particular chemical process.  Thermochemistry, however, does not predict how fast a reaction will occur.
  10. 10. THANKYOU

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