Physical Chemistry

Heat of Formation

Heat of Formation ❒ The heat of formation of a compound is defined as:The change in enthalpy that takes place when one mole of the compound is formed from its elements. ❒ It is denoted by ΔHf . For example, the heat of formation of ferrous sulphide and acetylene may be expressed as: ❒ Similarly, the …

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Enthalpy of a Reaction

Enthalpy of a Reaction ❒Thermochemical measurements are made either at (a) constant volume or (b) constant pressure. The magnitudes of changes observed under the two conditions are different. ❒ The change in internal energy (ΔE): is the heat change accompanying a chemical reaction at constant volume because no external work …

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MCQ on Chapter: First Law of Thermodynamics

1. The study of the flow of heat or any other form of energy into or out of a system undergoing physical or chemical change is called_______ (a) thermochemistry  (b) thermokinetics (c) thermodynamics (d) thermochemical studies Answer. (c) 2. Thermodynamics is applicable to_______ (a) microscopic systems only  (b) macroscopic systems …

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Adiabatic Expansion of an Ideal Gas

Adiabatic Expansion of an Ideal Gas ❒ A process carried in a vessel whose walls are perfectly insulated so that no heat can pass through them, is said to be adiabatic.❒ In adiabatic process there is no heat exchange between a system and surroundings, and q = 0. ❒ According …

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Molar Heat Capacities

Molar Heat Capacities ❒ By heat capacity of a system we mean the capacity to absorb heat and store energy. As the system absorbs heat, it goes into the kinetic motion of the atoms and molecules contained in the system. This increased kinetic energy raises the temperature of the system. …

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Enthalpy of A System

Enthalpy of A System ❒ In a process carried at constant volume (say in a sealed tube), the heat content of a system is the same as internal energy (E), as no PV work is done.  ❒ But in a constant-pressure process, the system (a gas) also expends energy in …

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Joule-Thomson Effect

Joule-Thomson Effect ❒ Joule and Thomson (later Lord Kelvin) showed that when a compressed gas is forced through a porous plug into a region of low pressure, there is appreciable cooling. ❒ The phenomenon of producing lowering of temperature when a gas is made to expand adiabatically from a region …

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First law of Thermodynamics + solved problems

Internal Energy ❒ A thermodynamic system containing some quantity of matter has within itself a definite quantity of energy. This energy includes not only the translation kinetic energy of the molecules but also other molecular energies such as rotational, vibrational energies. The kinetic and potential energy of the nuclei and …

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Work, First Law of Thermodynamics

  Nature of Heat and Work  When a change in the state of a system occurs, energy is transferred to or from the surroundings. This energy may be transferred as heat or mechanical work.  We shall refer the term ‘work’ for mechanical work which is defined as: force × distance. …

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Thermodynamic Processes

  Thermodynamic Processes ❒  When a thermodynamic system changes from one state to another, the operation is called a Process. ❒ These processes involve the change of conditions (temperature, pressure and volume). ❒ The various types of thermodynamic processes are: (1) Isothermal Processes (2) Adiabatic Processes (3) Isobaric Processes (4) …

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Hybridization and Shapes of Molecules

  ❒ In the previous subject we talk about the concept of Hybridization and the types of Hybridization, but in this subject we will talk about Hybridization and Shapes of Molecules. ❒ Diatomic molecules must all be invariably linear but tri-and tetra-atomic molecules have several possible geometrical structures. In this …

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Concept Of Hybridization

     While formation of simple molecules could be explained adequately by overlap of atomic orbitals, the formation of molecules of Be, B and C present problems of greater magnitude having no solution with the previous theory. To explain fully the tendency of these atoms to form bonds and the …

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