Amagat law
Amagat law: For a mixture of non-reacting gases the sum of partial volumes of these gases is equal to total volume of the mixture at constant temperature and pressure. Example5. Calculate the volume occupied by 1.0 g of argon at 300 K and pressure. ). Solution: no. of moles of argon, (m = mass of substance, M = Mol. Wt. of substance) According to ideal gas equation, PV =...
read moreFormulas of Gaseous State
Boyle’s law, (At constant temperature) Charle’s law; Gas equation, Ideal gas equation, PV = nRT. Avogadro’s hypothesis; (At const. temperature and pressure) Dalton’s Law, Graham’s law, Kinetic gas equation; Root mean square velocity; Average velocity; Most probable velocity U : v : = 1.0 : 0.9213 : 0.8177 : v : u = 1.0 : 1.128 : 1.234 Van der Waals equation, Critical...
read moreGay-Laussac’s law
Gay-Laussac’s law (1809): according to this law, “when gases react, the volume of these gases, and the volumes of the product formed (if gaseous) are in simple whole number ratio to each other”. E.g. The ratio 1 : 1 : 2 (a simple ratio) Example 1. An iron cylinder contains helium at a pressure of 240 kPa at 300 K. The cylinder can withstand a pressure of Pa. The room in which cyliner is placed catches fire. Predict whether the cylinder will blow up before it melts or not? (M.P. of the cylinder I800 K) Solution: According to pressure...
read moreLimitations of Van der waal’s equation
Limitations of Van der waal’s equation (i) The value of ‘b’ is not constant but varies with pressure and temperature. (ii) The value of is not equal to 3b, but actually it is equal to, in some case; and in other cases 2b. (iii) The value of is not equal to but it is ususlly more than 3 for most of the gases. Inversion Temperature: It is the temperature above which a gas warms up in adiabatic expansion of a gas from high pressure to low pressure. It is denoted by and is related with van der Waals constants...
read moreCritical Constants
Critical Constants The critical temperature, Tc, is characteristic of every gas and may be defined as: “The temperature below which the continuous increase of pressure on a gas ultimately brings about liquefaction and above which no liquefaction can take place no matter what so ever pressure be applied”. The pressure required to liquefy the gas at critical temperature is called critical pressure and the volume occupied by 1 mole of gas under these conditions is called the critical volume. Van der Waals equation may be written as: ...
read moreIdeal and Real Gases
(A) Ideal Gas An ideal or perfect gas is one which obeys Boyle’s and Charle’s laws rigidly for all values of pressure and temperature. The chief characteristics of an ideal gas are as follows: (i) At constant temperature the product of pressure and volume, PV should is constant and should not vary with pressure i. e., if a graph is plotted between PV and P at constant T, the curve obtained should be a straight line. (ii) When the temperature of ideal gas is decreased at constant pressure, its volume continuously decreases...
read moreVan der waal’s equation
Van der waal’s equation Thought the equation PV=RT was arrived at first experimentally and then theoretically, yet it fails to explain the behaviour of real gases. van der Waals attributed the deviation of real gases from gas equation to the following faulty assumptions of the kinetic theory: (i) The actual volume of the gas molecules is negligible as compared with the total volume of the gas. (ii) The gas molecules do not exert any appreciable attraction on each other. Both these assumptions are not true at high pressure and low...
read moreHeat Capacity of gases
Specific and molar heat capacity of gases Specific heat (or heat capacity) of a substance may be defined as the quantity of heat required to raise the temperature of 1 g of that substance by . it is expressed in calories or joules. Molar heat capacity may be defined as : Molar heat capacity = Sp. Heat × Mol. Mass Since the gases expand on heating, hence molar heat capacity of gases is termed as follows: (i) Molar heat capacity at constant pressure (Cp): it is the amount of heat in calories required to raise the temperature of one mole of a...
read moreMolecular Velocity
Molecular Velocities In kinetic theory of gas the velocity of molecules is expressed in the following three terms (i) Root-mean square velocity or R.M.S. Velocity: It may be defined as, “The square root of the mean value of the squares of the velocities of all molecules”. It is denoted by u. If are the velocities for n molecules, then (ii) The average velocity is the arithmetic mean of the velocities of all molecules. It is denoted by v and is given by the following equation: [ Average velocity (v) = 0.9213 x R. M. S. velocity...
read moreKinetic Theory of Gases
Kinetic theory of gases D. Bernaulli (1738) forwarded this theory which was developed by Clausius, Maxwell, Boltzmann, Kelvin etc. The following are the main postulates of kinetic theory of gases: (i) Every gas consists of very large number of minute (tiny) particles called molecules. The actual volume of these molecules is negligible as compared to the total volume of the gas. (ii) The molecules of a gas are not stationary but are always in a state of rapid random motion in all possible directions with widely differing velocities....
read more