Physical Chemistry

Gibbs Helmholtz Equations – These are two equations derived by J.W. Gibbs and H.Von Helmholtz and are known as Gibbs Helmholtz equations. – One equation can be expressed in terms of changes in free energy (ΔG) and enthalpy (ΔH), while the other can be expressed in terms of changes in …

– In this topic, we will discuss The Carnot Cycle : Definition, Theorem, Efficiency, Derivation and Sovled problems. The Carnot cycle – In 1824 Sadi Carnot proposed a theoretical heat engine to show that the efficiency was based upon the temperatures between which it operated. – Carnot’s imaginary engine could …

Definition of entropy – Entropy is a thermodynamic state quantity that is a measure of the randomness or disorder of the molecules of the system. – The symbol of entropy is S, while the change in disorder accompanying a process from start to completion is represented by ΔS.  – The entropy …

– In this topic, we will discuss the Macromolecules : Definition and Molecular Weight What are Macromolecules? – Colloidal solutions are formed by aggregation of atoms or molecules to give particles of colloidal size. – Macromolecules are substances which are themselves composed of giant molecules and dissolve in a solvent …

Second Law of Thermodynamics: MCQ Quiz with answers – In this subject, you will find 49 questions and answers MCQ on The Second Law of Thermodynamics. 1. A process which proceeds of its own accord, without any outside assistance, is called  ____ . (a) non-spontaneous process (b) spontaneous process (c) …

– In this topic, we will discuss The Applications of Colloids. Applications of Colloids – Colloids play an important role in our daily life and industry. – A knowledge of colloid chemistry is essential to understand some of the various natural phenomena around us. – Colloids make up some of …

– In this topic, we will discuss The Gels : Defination, Types, and Properties. What are Gels? – A gel is a jelly-like colloidal system in which a liquid is dispersed in a solid medium. – For example, when a warm sol of gelatin is cooled, it sets to a …

Defination of Emulsions – Emulsions are liquid-liquid colloidal systems. – In other words, an emulsion may be defined as a dispersion of finely divided liquid droplets in another liquid. – Generally one of the two liquids is water and the other, which is immiscible with water, is designated as oil. …

– In this subject, we will discuss the Associated Colloids. Associated Colloids – The molecules of substances as soaps and artificial detergents are smaller than the colloidal particles. However in concentrated solutions these molecules form aggregates of colloidal size. – Substances whose molecules aggregate spontaneously in a given solvent to …

Electrical Properties of Sols – In this topic we will discuss the Electrical Properties of Sols as follow: (1) The sol particles carry an electric charge. (2) Electrophoresis. (3) Electro-osmosis. (4) Coagulation or Precipitation. (5) Protective action of sols. (6) Origin of charge on sol particles. (1) The sol particles …

Kinetic Properties of Sols – In this topic, we will discuss Kinetic Properties of Sols. Brownian Movement – When a sol is examined with an ultramicroscope, the suspended particles are seen as shining specks of light. – By following an individual particle it is observed that the particle is undergoing …

Optical Properties of Sols – In this topic, we will discuss Optical Properties of Sols as follow: Sols exhibit Tyndall effect Ultramicroscope shows up the presence of individual particles Sol particles can be seen with an Electron microscope (1) Sols exhibit Tyndall effect – When a strong beam of light …

– In this topic, we will discuss Preparation of Sols, Purification of Sols and its colors Preparation of Sols – Lyophilic sols may be prepared by simply warming the solid with the liquid dispersion medium e.g., starch with water. – On the other hand, lyophobic sols have to be prepared …

– In this topic, we will discuss The Lyophilic and Lyophobic sols : Defination, Characteristics, and Comparison. Defination of Lyophilic and Lyophobic sols – Sols are colloidal systems in which a solid is dispersed in a liquid. – These can be subdivided into two classes : Lyophilic sols (solvent-loving) Lyophobic …

– In this topic, we will discuss the colloids: definition, History and Types History of colloids – Thomas Graham (1861) studied the ability of dissolved substances to diffuse into water across a permeable membrane. – He observed that crystalline substances such as sugar, urea, and sodium chloride passed through the …

– In this topic, we will discuss Acid-Base catalysis: definition, Examples and Mechanism. Acid-Base catalysis – A number of homogeneous catalytic reactions are known which are catalysed by acids or bases, or both acids and bases.  These are often referred to as Acid-Base catalysts. – Arrhenius pointed out that acid …

– In this topic, we will discuss the Magnetic Shielding by Electrons Magnetic Shielding by Electrons – Up to now, we have considered the resonance of a naked proton in a magnetic field, but real protons in organic compounds are not naked. – They are surrounded by electrons that partially …

Theories of Catalysis – There are two main theories of catalysis: (1) Intermediate Compound Formation theory. (2) The Adsorption theory. – In general, the Intermediate Compound Formation theory applies to homogeneous catalytic reactions and the Adsorption theory applies to heterogeneous catalytic reactions. The Intermediate Compound Formation Theory – The Intermediate …

– In this topic, we will discuss Autocatalysis, Catalytic poisoning and Negative Catalysis. Catalytic poisoning – Very often a heterogeneous catalyst in rendered ineffective by the presence of small amounts of impurities in the reactants. – A substance which destroys the activity of the catalyst to accelerate a reaction, is …

Introduction to NMR  – Nuclear magnetic resonance spectroscopy (NMR) is the most powerful tool available for organic structure determination. – Like infrared spectroscopy, NMR can be used with a very small sample, and it does not harm the  sample. – The NMR spectrum provides a great deal of information about …