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  Heat of Combustion – The heat of combustion of a substance is defined as The change in enthalpy of a system when one mole of the substance is completely burnt in excess of air or oxygen. – It is denoted by ΔHc. – For example, the heat of combustion …

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 …

– The heat of reaction or enthalpy changes accompanying chemical reactions are expressed in different ways, depending on the nature of the reaction. These are discussed below. (1) Heat of Formation – The heat of formation of a compound is defined as The change in enthalpy that takes place when …

– In this subject, the Variation of heat of reaction with temperature will be discussed. Heat of Reaction or Enthalpy of Reaction – The heat of a reaction is simply the amount of heat absorbed or evolved in the reaction. – We also know that the amount of heat absorbed …

– For reactions involving solids and liquids only the change in volume (ΔV) is very small and the term P × ΔV is negligible. For such reactions, the Change of Enthalpy of Reaction ΔH is equal to ΔE. Enthalpy of Reaction – Thermochemical measurements are made either at (a) constant …

MCQ on the First Law of Thermodynamics – In this subject, you will find 50 questions and answers MCQ on the First law of Thermodynamics 1. The first law of thermodynamics is_______ (a) the total energy of an isolated system remains constant though it may change from one form to …

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 the adiabatic process there is no heat exchange between a system and surroundings, and q = 0. …

Molar Heat Capacity – 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 …

– Enthalpy (H) is the total heat content of a system at constant pressure and is equivalent to the internal energy E plus the PV energy. Enthalpy of A System – In a process carried at constant volume (say in a sealed tube), the heat content of a system is …

– The phenomenon of producing a lowering of temperature when a gas is made to expand adiabatically from a region of high pressure into a region of low pressure is known as the Joule-Thomson Effect or Joule-Kelvin Effect Joule-Thomson Effect – Joule and Thomson (later Lord Kelvin) showed that when …

– The first law of Thermodynamics states that The total energy of an isolated system remains constant though it may change from one form to another. Internal Energy – A thermodynamic system containing some quantity of matter has within itself a definite quantity of energy. – This energy includes not …

– In physics, mechanical work is defined as force multiplied by the distance through which the force acts. – In elementary thermodynamics, the only type of work generally considered is the work done in the expansion (or compression) of a gas Nature of Heat and Work  – When a change …

– Thermodynamic Processes involve the change of conditions (temperature, pressure, and volume). Thermodynamic Processes – When a thermodynamic system changes from one state to another, the operation is called a Process. – Thermodynamic Processes involve the change of conditions (temperature, pressure, and volume). – The various types of thermodynamic processes …

What is Thermodynamics? – Thermodynamics is The study of the flow of heat or any other form of energy into or out of a system as it undergoes a physical or chemical transformation. – In studying and evaluating the flow of energy into or out of a system, it will …

Molecular Orbitals for Heteronuclear Diatomic Molecules – In the previous subject, we talk about but electronic structures and bonding properties of some of The homonuclear diatomic molecules. but in this subject, we will talk about Molecular Orbitals for Heteronuclear Diatomic Molecules (MO Theory) – When two different atoms are bonded …

Molecular Orbitals for Homonuclear Diatomic Molecules – In the previous subject, we talk about but electronic structures and bonding properties of some of The Heteronuclear Diatomic Molecules. but in this subject, we will talk about Molecular Orbitals for Homonuclear Diatomic Molecules (MO Theory) – After having discussed the basic principles …

MCQ on Chemical Bonding – Orbital Theory – In this subject, you will find 46 questions and answers MCQ on Chemical Bonding – Orbital Theory 1. When a chemical bond between two atoms is formed, the potential energy of the system_______ (a) decreases (b) increases (c) remains the same (d) …

Molecular Orbital Theory – The molecular orbital theory proposed by Hund and Mulliken in 1932 explains the formation of a covalent bond in a better way.  – According to molecular orbital theory all atomic orbitals of the atoms participating in molecule formation get disturbed when the concerned nuclei approach nearer. …

MCQ on the structure of the atom – In this subject, you will find 50 questions and answers MCQ on Chapter structure of atom – wave mechanical approach 1. The number of unpaired electrons in oxygen atom is_______ (a) 1 (b) 2 (c) 3 (d) 4 Answer. (b) 2. The …

– In this subject, we will discuss the difference Between Electronegativity and Electron Affinity Electron Affinity  – A neutral atom can accept an electron to form a negative ion. In this process, in general, energy is released. – The electron affinity (EA) of an element is the amount of energy released …