Physical Chemistry

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 …

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 …

 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 …

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. …

Spontaneous Processes A process which proceeds of its own accord, without any outside assistance, is termed a spontaneous or natural process. The reverse process which does not proceed on its own, is referred to as a nonspontaneous or unnatural process. In general, the tendency of a process to occur naturally …

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) …

  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 …

Bond energy  ❒ When a bond between two atoms is formed, there is a release of energy. The same amount of energy is absorbed when the bond is broken. ❒The bond energy is defined as: the average amount of energy required to break all bonds of a particular type in …

Hess’s Law of Constant Heat Summation ❒ We have already seen that heat changes in chemical reactions are equal to the difference in internal energy (ΔE) or heat content (ΔH) of the products and reactants, depending upon whether the reaction is studied at constant volume or constant pressure.  ❒ Since …

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 …