Title 3.CHEMICAL EQUILIBRIUM (GN REDDY-MDP) FINAL.pdf ✅

NISHITH Multimedia India (Pvt.) Ltd., 111 JEE MAINS - CW - VOL - I JEE ADVANCED - VOL - II CHEMICAL EQUILIBRIUM NISHITH Multimedia India (Pvt.) Ltd., CHEMICAL EQUILIBRIUM i) Predicting extent of reaction ii) Predicting direction of change iii) Calculation of equilibrium concentration Application of equilibrium constant Different forms of equilibrium Constant The concentration of gases can be expressed in different ways. The following relations exist be- tween equilibrium constants.     H P X H P C K K p K K RT     EQUILIBRIUM TYPE OF EQUILIBRIA Physical equilibrium 1. Solid – liquid 2. Liquid – gas 3. Solid – liquid – gas 4. Solubility of solute in solution 5. Solubility of gas in solution Chemical equilibrium 1. Reaction Quotient 2. Significance of equilibrium constant 3. Law of mass action 4. Homogeneous equilibria i) degree of dissociation from vapourdensity measure ment ii) relation between and 5. Equilibrium constant and 6. Heterogeneous equilibrium 7. Temperature dependence of equilibrium constant 8. Kinetics and equilibrium constant c k p k p k c k SYNOPSIS Lechatelier's principle * Effect of following factor's on equilibrium * Once pressure temperature catalyst inert gas Temperature dependence van't Hoff's equation Understanding equilibrium From kinetic's approach (Guldberg and Waage approach)
CHEMICAL EQUILIBRIUM 112 NISHITH Multimedia India (Pvt.) Ltd., JEE ADVANCED -VOL - II NISHITH Multimedia India (Pvt.) Ltd.,   tan 1 2 K N     tan 2 2 K O   * Mixture of non reacting gases x p  ' ' x is molefraction of gas in solution ‘p’ is partial pressure of gas (p) x k P  ' ; 1 . ' P x K  ; 1 ' K K H  K H  Henry’s constant K H of 2 N in bar at 293 K and 303 K is 76.48 and 88.64 Higher the henry’s constant value lower the solubility of gas in liquid * Equilibrium and Thermodynamics An equilibrium state is dynamic state at which there is no change in macroscopic properties (Chemical Composition, Temperature and Pressure) of the state., According to thermodynamics a system in equilibrium possesses no driving force for a change in eitherdirection of reversible reaction. Spontaneity of any reaction depends on free energy change of that reaction. At a given temperature and pressure a reaction always tend to move in direction in free energy change is decreasing. The reactants react till a state of minimum free energy is attained and this state represent equilibrium state of reversible reaction. Progress of reversible reaction.   n K K P P X     n K K RT P C   KP is independent of pressure where as x k (equilibrium constant in terms of molefraction) will depend on pressure if   n 0 * Henry's Constant Most of the gases are soluble in water or in some other liquid to a more or less extent solubility is generally expressed in terms of absorption coefficient Solubility of gases in liquids equilibrium is governed by HenryslawAs temperature in- creases solubility decreases as dissolution is exothermic Absorption coefficient = Volumeof gas in ml at S T P . . Volumeof liquid P atm  Effect of pressure on the solubility of gas in liquid is given by henryslaw. Let mass of the gas dissolved per unit volume of solvent (m) Let ‘P’ is pressure of gas which is in equilib- rium with solvent. m P  m K P  . Magnitude of ‘K’ depends on nature of gas , solvent temperature and units of pressure. 1 1 2 2 m p m p  Slope of line tan  K
NISHITH Multimedia India (Pvt.) Ltd., 113 JEE MAINS - CW - VOL - I JEE ADVANCED - VOL - II CHEMICAL EQUILIBRIUM NISHITH Multimedia India (Pvt.) Ltd., * Equiblibrium constant as per kinetics       K f A B C g g g K b     f b      d A K A K B C dt      0 m d A At eq dt   . / a K Ae RT     .e / Ea f K A RT f f     .e / Ea b K A RT b b       . / . / a f f f eq a b b b K A e RT K K A e RT     . / H K A e RT       H E E a f a b    ln ln 1 1 H k A RT    ln ln 2 2 H k A RT    2 1 1 ln 1 1 2 k H k R T T            Sequential equilibrium S g g      A B C   a x  x x y   g g    C D  x y  y   1 K x x y C   2 y K C x y   simultaneous equilibrium s x   g g    A B    p1 k x y x   x+y x s Y   g g    A C   p2 K x y y   y+x y 1 2 p p K x K y  2 2 P x y total   Phase euilibrium Phase diagram for water curve oc must meet the other two curves at triplepoint ‘O’ A long OA water and vapour, a long OB ice and vapour and along OC ice and water co exist in equilibrium. At the point ‘O’ three phases namely ice, water and vapour co exist. Three phases can co exist in equilibrium only at a definite temperature and pressure repre- sented by the point ‘O’ The vapourpressure at ‘O’ is 4.58 mm and the temperature in 0 0.0075 C * Phase diagram for CO2
CHEMICAL EQUILIBRIUM 114 NISHITH Multimedia India (Pvt.) Ltd., JEE ADVANCED -VOL - II NISHITH Multimedia India (Pvt.) Ltd., Phase diagram of CO2 resembles that of water in showing three distinit areas for solid liquid and gaseousphase but it differs essentially from the later in several arpects. The fusion curve slopes away from the pres- sure axis. This indicated that increase of pressure raises the melting point of solid CO2 Specific volume of liquid CO2 is greater than that of solid CO2 . Solid CO2 can exist in equilibrium with its liquid that is it can melt only at very high pressure equal to to 5.2 atm. This is unlike water system in which ice and water can exist in equilibrium. even at very low pressure 4.58 mm of Hg Vapour pressure of solid CO2 even at extermely low temperature is very high and many times. higher than that of ice even at 1 atm pressure CO2 gas can be directly solidi- fied in cooling to 0 78 C . Hence solid CO2 is known as dryice * Evaporation & Relative humidity concentration of solution is carried out at a temperature below 0 100 C under reduced pressure as decrease in external pressure decreases the boiling point of water. Conditions under which a hydrated salt will lose water to the atmosphere or which a salt will absorb water from atmosphere. Efflorescent salt will lose water to the atmo- sphere if watervapour pressure in equilibrium with the salt is greater than partial vapourpressure of water in the atmosphere on the other hand a salt will absorb moisture from the atmosphere if the water vapour pressure in equilibrium with the salt is less than the water vapour pressure in the atmosphere. Relative humidity = PartialVapour pressureof water air in the EquilibriumVapour pressureof water at sametemp Equilibrium condition for any system is that chemical potential of each constituent through out the system must be same . If there are several phases then the chemical potential of each constituent in every phase must have the same value Phase is defined as that portion of the system which is uniform among its submacroscopic statebut is definitely separated from other such portions of the system by well defined bound- aries Mixture of solids or two immiscible liquids can form separate phases Mixture of gases is one phase as it is homogeneous SYSTEM Exercise -1 How many phases are present in the following equilibrium ?   3 s caco  s g  2  cao co  Answer : In the a bove equation , two solids are of diffrent structure and are separated by definite boundaries . There are three phases that is two solids and one gas. Exercise -2 An iceberg is floating in the lake . If one considers the lake , ice berg and atmosphere as a one system what are the number of phases? Answer : I ceberg is a solid form of water ,lake is liquid water and atmosphere contains water vapours and other gases . so there are three phases solid liquid and vapour. EXERCISE -3 If at any temperature and pressure liquid water is in equilibrium with water vapour and solid ice then ice  2   0 H l   H vapour 2 0   where  is chemical potential Chemical potential of any compenent is defined