Physical Chemistry

Vapour Pressure , Factors affecting on Vapour Pressure

Vapour Pressure When a liquid is placed in an open vessel, it evaporates. The molecules in the liquid are moving with different kinetic energies. The molecules that possess above-average kinetic energies can overcome the intermolecular forces that hold them in the liquid. These energetic molecules escape from the liquid surface …

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Intermolecular Forces in Liquids

 Intermolecular Forces in Liquids Intermolecular forces in liquids are collectively called van der Waals forces. These forces are essentially electrical in nature and result from the attraction of charges of opposite sign.  The principal kinds of intermolecular attractions are: (1) Dipole-dipole attractions (2) London forces (3) Hydrogen bonding.    The relative …

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General Characteristics of Gases

All matter exists in three states: gas, liquid and solid.   A molecular level representation of gaseous, liquid and solid states is shown in the following Fig:     A gas consists of molecules separated wide apart in empty space. The molecules are free to move about throughout the container. …

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MCQ on Chapter: Thermochemistry

1. The branch of chemistry which deals with the heat changes caused by chemical reactions is called _______ (a) thermodynamics (b) thermal chemistry (c) thermochemistry (d) none of these Answer. (c) 2. In an exothermic reaction, the internal energy of the products is _______ internal energy of the reactants. (a) …

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Measurement of The Heat of Reaction

  Measurement of The Heat of Reaction ❒The experimental measurement of the heat of reaction or enthalpy change is known as calorimetry. ❒ The name (calorimetry) evidently finds its origin in the unit of heat–the calorie. ❒ The heat given out or absorbed in a chemical reaction is measured in …

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Energy Changes During Transitions or Phase Changes

Energy Changes During Transitions or Phase Changes ❒ The three states of matter – solid, liquid and gas differ from one another in the arrangement of their constituent particles. ❒ The magnitudes of intermolecular forces acting between the particles in these states are also different. ❒ It is a common observation that when …

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Heat of Combustion

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. As for example, heat of combustion of methane is – 21.0 kcal …

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