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arindameducationusc

  • one year ago

Thermodynamics basics Tutorial 1.1

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  1. arindameducationusc
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    \(\Huge\color{red}{Thermodynamics} \) It deals with energy exchange b/w system & surrounding. It predicts the feasibility or spontaneity of a process or a reaction. It relates energy in different physical or chemical process. \(\Large\color{blue}{Limitations~of~Thermodynamics} \) 1) It relates the only macroscopic property of system. It cannot be applied on atomic or molecular level 2) It never tells about time involved in the process. \(\Large\color{blue}{Some~Important~terms } \) System=> It is part of universe under investigation Surrounding=> rest part of universe. Universe=System+Surrounding \(\Large\color{blue}{Type~of~System} \) 1)Open system=> which exchanges mass as well as energy with the surrounding. Eg=> a cup of tea, boiler, human body, any living thing, earth, etc 2)closed system=> which exchanges energy but not mass with surrounding. example=> Electrochemical cell, liquid cooling system of an automobile 3) Isolated system=> Which does not exchange energy as well as mass with the system. Eg=>Thermoflask, Universe,etc It is impossible to create a perfectly isolated system but a system insulated can be considered as isolated.

  2. arindameducationusc
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    \(\Large\color{blue}{State} \) When all the macroscopic properties of a system have some fixed values, the system is called in particular state. \(\Large\color{blue}{Thermodynamic~properties} \) The physical quantities used to define the states of system are called Thermodynamic Properties. Eg=> Pressure, Volume, Temperature, etc are properties of a gaseous system.

  3. arindameducationusc
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    \(\Large\color{red}{**Type~of~properties} \) * Those property independent to the quantity of a system are called \(\Large\color{blue}{Intensive~property} \) Example=> Pressure, Temperature, Molar mass, Specific Volume (Volume/Mass), Molar Internal Energy, molar enthalpy, specific resistance, molar conductivity, equivalent conductivity, All concentration terms( molality, normality, formality, %by mass,% by volume,%by strength,ppm,volume strength of H2O2, %Labelling of Oleum), Emf of cell, specific heat capacity, molar heat capacity, refractive index, surface tension, viscosity, boiling point, vanderwaal gas constant, coefficient of friction, Di electric constant, Permitivity, Vapour Pressure, Conductivity, Resistivity. \(\Large\color{blue}{Extensive Property} \) Those properties depending on quantity of system called Extensive Property example=> mass, volume, mole, Kinetic Energy, Potential Energy, Internal Energy, Enthalpy, Gibbs Free Energy, Resistance, Conductance, Heat capacity, Helm-Holmes free Energy.

  4. arindameducationusc
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    \(\large\color{blue}{if~you~do~not~understand~extensive~and~intensive} \) \(\large\color{blue}{leave~it ~for~now,~focus~other~topics} \)

  5. arindameducationusc
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    Further the variation of thermodynamic property is categorized into 2 categories=> 1) State function=> depends on only initial & final state of function no matter what path followed during process. Eg> Internal Energy, Enthalpy, Temperature 2)Path Function=> depends on path of the process Example> work done, Heat. Thermodynamic process are categorised into 2 categories on basis of direction of change=> 1)irreversible 2)reversible

  6. arindameducationusc
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    \(\Large\color{red}{Thermodynamic~Processes} \) Isochoric process \[V=constant\] Isobaric process \[ P=constant\] Adiabatic process \[\Delta q=0\] Isothermal process, \[T=constant\]

  7. arindameducationusc
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    \(\Large\color{red}{Entropy} \) One of the most important things to remember about thermodynamics is that low energy states are more stable than higher states. Fundamentally the universe prefers low energy states, it tends towards disorder. When we talk about disorder, we use entropy. Everything tends towards maximum entropy. When we talk about difference of entropy of products and entropy of reactants, we use ΔS. If ΔS is negative, the reaction has lost entropy; the products are more orderly then the reactants. If ΔS is positive, the reaction has gained entropy; the products are less orderly than the reactants.

  8. arindameducationusc
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    |dw:1440396764090:dw|

  9. arindameducationusc
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    Always think the universe is lazy so they are most stable at states of low energy and states of high entropy |dw:1440397310909:dw|

  10. arindameducationusc
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    \(\Large\color{red}{Enthalpy} \) Because the universe tends towards low energy, chemical reactions release energy that set energy free-are favoured in the universe. When we talk about energy states, we use the term enthalpy (H). So the universe likes reactions in which enthalpy decreases, reactions in which ΔH is negative. These reactions are called \(\Large\color{red}{exothermic} \), and they result in the release of energy in the form of heat. If, however the enthalpy of products is greater than the enthalpy of reactants, then ΔH is positive and the reaction is said to be \(\Large\color{blue}{endothermic} \). Endothermic reactions require the input of energy in order to take place.

  11. arindameducationusc
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    \(\Large\color{blue}{Spontaneity~and~Gibbs~Free~Energy} \) A spontatneous reaction is one that occur at a given temperature without the input of energy. What determines whether a reaction will or won't occur spontaneously? The combination of ΔH and ΔS is called Gibbs free Energy which determines and is symbolised by ΔG. ΔG=ΔH-TΔS (T in Kelvin)

  12. arindameducationusc
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    *If ΔG for the reaction is negative, then that reaction occurs simultaneously in the forward direction. If ΔG for the reaction is positive, then the reaction occurs simultaneously at that temperature in reverse direction. If ΔG =0, then the reaction is in equilibrium.

  13. arindameducationusc
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    \(\Large\color{red}{Modes of Energy} \) \(\Large\color{blue}{1) heat=>} \) Energy transfer which occurs due to temperature difference. It is a path function & extensive property but not thermodynamic property. \(\Large\color{blue}{1) Work=>} \) It is defined as form of energy which appears by change in boundary of system. It is also a path function & extensive property but not thermodynamic property. Actually mode of energy depends on choice of system

  14. arindameducationusc
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    \(\Large\color{blue}{IUPAC~SIGN~CONVENTION} \) Any form of Energy given to the system is taken as positive & any form of Energy released by the system is taken as negative. Heat released by the system=-ve Heat absorbed by the system=+ve Work done by the system=-ve Work done on the system=+ve

  15. arindameducationusc
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    \(\Large\color{red}{Internal Energy} \) Every substance possess a fixed quantity of energy which depends upon its chemical nature and its state of existence. It is denoted by U. The various forms of energy which contribute towards te internal energy are translational energy, rotational energy, vibrational energy, electronic energy, nuclear energy f constituent atoms, potential energy of the molecules due to molecular interactions, chemical bond energy due to existence of bonds between atoms within molecules,etc. But we are interested mostly in "change in Internal Energy" which occurs during chemical reactions. It is extensive property It is a state function.

  16. arindameducationusc
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    \(\Large\color{red}{First~Law~of~Thermodynamics} \) According to 1st law of thermodynamics, energy can neither be created nor destroyed. If a system is applied 'q' amount of heat, then the internal energy of the system increases and becomes \[U _{1}+q\] Now if work is done on the system, then its internal energy further increases and becomes \[U _{2}\] So, mathematically, \[U _{2}=U _{1}+q+w\] \[U _{2}-U _{1}=q+w\] \(\Large\color{red}{[\Delta U=q+w]} \)

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