Physical Chemistry

Law of Mass action – Two Norwegian chemists, Guldberg and Waage, studied experimentally a large number of equilibrium reactions. In 1864, they postulated a generalisation called the Law of Mass action. – Law of Mass action states that : the rate of a chemical reaction is proportional to the active …

Chemical Equilibrium is the state of a reversible reaction when the two opposing reactions occur at the same rate and the concentrations of reactants and products do not change with time. Nature of Chemical Equilibrium : its definition – Let us consider the reaction A + B ↔ C + …

Online MCQ test on First law of thermodynamics – In this topic we offer you, online MCQ test in the fundmental of First law of thermodynamics. – It is a simple test to measure the strength of your knowledge in the basics of understanding the topics of First law of …

Laws of Osmotic Pressure – From a study of the experimental results obtained by Pfeffer, van’t Hoff showed that for dilute solutions : (a) The osmotic pressure of a solution at a given temperature is directly proportional to its concentration. (b) The osmotic pressure of a solution of a given …

Theories of Osmosis – Here we will discuss some theories of osmosis. – Several theories have been advanced to explain the action of a semipermeable membrane. – It is probable that the mechanism depends on the particular type of membrane used and also on the nature of the solute and …

Determination of osmotic pressure – The osmotic pressure of a given solution can be determined experimentally by the methods detailed below. – The apparatus used for the purpose is often referred to as osmometer. (1) Pfeffer’s Method – The apparatus used by Pfeffer (1877) for determination of osmotic pressure is …

Diffusion and Osmosis – Just as a gas can diffuse into vacant space or another gas, a solute can diffuse from a solution into the pure solvent. – If you pour a saturated aqueous solution of potassium permanganate with the help of a thistle funnel into a beaker containing water, …

The subject of Measurement of freezing point Depression will be discused FREEZING POINT DEPRESSION Relation between Depression of Freezing point and Lowering of Vapour-pressure – The vapour pressure of a pure liquid changes with temperature as shown by the curve ABC, in Fig. – There is a sharp break at …

MEASUREMENT OF BOILING POINT ELEVATION – There are several methods available for the measurement of the elevation of boiling point. – Some of these are outlined below : (1) Landsberger-Walker Method This method was introduced by Landsberger and modified by Walker. Apparatus: – The apparatus used in this method is …

MEASUREMENT OF LOWERING OF VAPOUR PRESSURE (1) Barometric Method – Raoult measured the individual vapour pressure of a liquid and then the solution by this method. – He introduced the liquid or the solution into Toricellian vacuum of a barometer tube and measured the depression of the mercury level. – …

In this subject we will restrict our discussion to Raoult’s Law COLLIGATIVE PROPERTIES – Dilute solutions containing non-volatile solute exhibit the following properties : (1) Lowering of the Vapour Pressure (2) Elevation of the Boiling Point (3) Depression of the Freezing Point (4) Osmotic Pressure – The essential feature of …

SOLUTIONS OF SOLIDS IN LIQUIDS – Solutions of a solid substance in a solvent are most commonly met with. – The process of solution of a solid substance in a solvent is explained by the electrical forces operating between the molecules or ions of the solute and the molecules of …

SOLUTIONS OF LIQUIDS IN LIQUIDS – The solutions of liquids in liquids may be divided into three classes as follows: – We will now proceed to consider the more important properties of these three classes of solutions. SOLUBILITY OF COMPLETELY MISCIBLE LIQUIDS – Liquids like alcohol and ether mix in …

The subject of Solutions of gases in gases – Henry’s Law will be discused Types of Solutions – The common solutions that we come across are those where the solute is a solid and the solvent is a liquid. – In fact, substance in any three states of matter (solid, …

Concentration of A Solution – The concentration of a solution is defined as : the amount of solute present in a given amount of solution. – Concentration is generally expressed as the quantity of solute in a unit volume of solution. A solution containing a relatively low concentration of solute …

Optical Activity – Optical activity is one of imortant physcial properties of liqiuds – A beam of ordinary light consists of electromagnetic waves oscillating in many planes. – When passed through a polarizer (e.g., a Polaroid lens), only waves oscillating in a single plane pass through. – The emerging beam …

Refractive Index – The refractive index (n) of a substance is defined as the ratio of the velocity of light in vacuum or air, to that in the substance: – When a ray of light passes from air into a liquid, its direction is changed. This change of direction is …

Viscosity – Viscosity is the resistance of a liquid to flow. – A liquid may be considered to be consisting of molecular layers arranged one over the other. – When a shearing force is applied to a liquid, it flows. However, the forces of friction between the layers offer resistance …

Surface Tension – Surface Tension property of liquids arises from the intermolecular forces of attraction. – A molecule in the interior of a liquid is attracted equally in all directions by the molecules around it. – A molecule in the surface of a liquid is attracted only sideways and toward …

– The vapour pressure of a liquid is defined as the pressure exerted by the vapour in equilibrium with the liquid at a fixed temperature. Vapour Pressure – When a liquid is placed in an open vessel, it evaporates. – The molecules in the liquid are moving with different kinetic …