Chemqueries: November 2018

Thursday, 22 November 2018

Optical isomerism in coordination compound

What is optical isomerism?

Optical isomers is also called enantiomers and these are the pair of molecules or ions that are non- superimposable mirror images of each other.
                                                   Image result for optical isomerism

What does the term superimposable mean?

The term superimposable means that if one structure is laid over the other of the same molecule the position of all the atoms should be matched and these two are called non-superimposable mirror image of each other.
  • For example, if a pipette is placed in front of a mirror, the image reflected on the mirror is identical to the pipette itself. So, in this case, we say that pipette and its mirror image are superimposable with each other.
  • If the left hand is placed in front of a mirror, the image reflected on the mirror will look like the right hand. Thus we can say that left and right hand are the mirror image of each other but are non-superimposable when the left hand is placed over the right hand keeping the palms down, they do not match. This superimposable property of left and right hand is called handedness.
    The optical isomers have handedness and are said to be chiral.

What are chiral molecules?

  • The molecules which are optically active and rotate the plane polarized light towards left or right are known as chiral molecules.
  • If the plane polarized light is rotated to the right, the isomer is said to be dextrorotatory(d or +) and if it is rotated to the left, the isomer is said to be levorotatory(l or -).The d- and l- isomer of a chiral substance are called enantiomers.
  • An equimolar mixture of d- and l- isomer, called a racemic mixture.
  • The essential condition for a substance to be chiral(or optically active) is the substance must have non-superimposable mirror image and it don't have any plane of symmetry.

Optical isomerism in the square planar complex:

Why square planar compound does not  show optical isomerism?

  •  Square planar complex rarely show optical  isomerism whether all the four ligands are different are same because they have  all the four ligands and the metal cation in the same plane and hence have a plane of symmetry. 
  • How ever there are exceptionally some complexes which exhibit optical isomerism i.e. (isobutylenediamine) (meso-diphenylethylenediamine) palladium (II) or palladium(II) complex.

Tuesday, 20 November 2018

Stereoisomerism

  • The isomer in which same type and number of ligands coordinated to the metal atom or cation but with different spatial(spatial arrangement means an arrangement in space)arrangements are called stereoisomers.
  • Stereoisomerism is classified into two types i.e.
    1. Geometrical isomerism
    2. Optical isomerism

Geometrical isomerism:

  • Stereoisomers in which relative position or orientation of the ligand is different i.e. donor atom around the central metal cation is different are called geometrical isomers and the phenomenon is called geometrical isomerism.
  • Geometrical isomers cannot be interconverted without breaking the metal-ligand(M-L) bond.
  • Geometrical isomerism is shown by that compound which can be converted into its cis and transform.
  • The isomer in which two particular ligands occupy the adjacent position of each other is called cis- isomer and the isomer in which two adjacent ligands occupy an opposite position to each other is called trans -isomer.
  • Cis and trans isomer are different compounds with different properties like melting point, dipole moment, solubility, colours, and chemical properties.
  • Geometrical isomerism is most common in complexes having coordination number 4 and 6 but the complexes having coordination number 2 and 3 do not exhibit geometrical isomerism.
  • cis/trans-2-butene









  • But in the coordination compound, this type of isomerism is found mainly in the heteroleptic complex because here multiple geometrical arrangements of ligand around the central metal atom are possible.
  • Square planar complexes are coordination compounds with coordination number 4 having [MX2L2] type formula, where X and L are unidentate ligands. The two ligands X could either be adjacent to each other in a cis isomer or opposite to each other to form a trans isomer.
    Square planar complexes with MABXL type formula show three isomers-two cis and one trans.
  • Tetrahedral geometry does not display these isomers. However, octahedral complexes do show cis and trans isomerism. In complexes with formula [MX2L4] type, we can have the X ligands in the arrangement of cis or trans to each other.
  • We also observe this type of isomerism when bidentate ligands L–L [e.g., NH2 CH2 CH2 NH2 (en)] are present in complexes with [MX2(L–L)2] type formula. There is another type of geometrical isomerism that we find in octahedral coordination entities with [Ma3b3] type formula. An example is [Co(NH3)3(NO2)3].

  • Facial and Meridional isomer:

    • Facial isomers are those in which three donor atom of the same ligand occupies an adjacent position at the corner of an octahedral face. They have the ligand in the cis arrangement.
    • And we get meridional isomer when the position of the ligands are around the meridian of the octahedron. Here the ligands are in the trans arrangement .

    Session Quiz:
    1. The number of possible isomer for the octahedral complex ion [Co(en)Cl2Br2]- is _______ .
    2.What is the number of isomer exist for [Mo(C5H5N)3(CO)3]  ?




     

Sunday, 18 November 2018

Structural Isomerism

Before discussing about this topic please go through the link  and get idea about isomerism .https://chemqueries.blogspot.com/2018/11/isomerism-in-coordination-compound.html

Classification of  Structural isomerism:

1.Ionisation isomerism:

  • In these isomer there is exchange of ligand between coordination sphere and ionization sphere.
  • Here the chemical formula is same, only the ligands present inside and outside the coordination sphere are exchanged.
  • These isomers give different ions when dissolved in water.
  • For example
    [Co(NH3)5Br]SO4   and [Co(NH3)5SO4  ]Br  and show ionization isomerism. Here we noticed that in both the compound only sulphate ion and bromide ion are among themselves.
  • Some other examples are  ,
    [Co(NH3)5Cl]SO4   and   [Co(NH3)5SO4]Cl 
    [Co(NH3)5NO3]SO4   and   [Co(NH3)5SO4]NO3 
    [Co(en)2Cl(NO2)]SCN   and   [Co(en)2Cl(SCN)]NO2 

2.Hydrate isomerism:

  • Hydrate means the word water, so in this type of isomerism only the water molecule is exchanged between coordination sphere and ionization sphere.
  • When we dissolve these isomers in aqueous solution, they give different colour.
  • For example,
    [Cr(H2O)6]Cl3 (violet)    and    [Cr(H2O)5Cl]Cl2.H2O (pale, green)
  •  Here we all notice one thing that, number of water and chlorine molecule is same    in both the  compound. The only difference is that in 1st compound all the water molecule is present inside the coordination sphere but in second one five is present inside and one is present outside the  coordination sphere.

3.Linkage isomerism: 

  • Linkage isomerism is shown by ambidentate ligand(ligand that have two different donor atom).
  • Linkage isomerism arises when an ambidentate ligand can coordinate to a metal cation through either of the two donor atoms.
  • Lets take an ambidentate ligand
    NO2-  ion, it has two donor atom N-atom and  O-atom, it can coordinate to the metal cation either through nitrogen atom or through oxygen atom.
  • The linkage isomers containing NO2- as ligand are
               [Co(NH3)5(NO2)]2+     ( N-atom coordinate to Co3+ )
       and  [Co(NH3)5(ONO)]2+    ( O-atom coordinate to  Co3+ )

4.Coordination isomerism:

  • The compound in which both cation and anion are complex ions and there nay be exchange of ligands between these two complex ions are known as coordination isomer.
  • In the pairs of these isomers,the central metal cation in the two coordination sphere may be same or different.
  • Some examples are 
    [Co(NH3)6][Cr(CN)6]    and      [Cr(NH3)6][Co(CN)6]
    [Cu(NH3)4][PtCl4]     and     [Pt(NH3)4][CuCl4] 

5. Coordination position isomerism:

  • This type of isomerism is formed by the bridging complex and there is a exchange of ligand between two metal cations.
  • For example,
2098_Coordination Position Isomerism.png
  •  Here we can see that only ligands are exchange in between the coordination so here and ionization sphere.

6. Ligand isomerism: 

  • If the ligand itself exist in two or more isomeric form, then the complexes containing such type of ligand show ligand isomerism.
  • For exampleCH3 – CH – CH2         and       CH3 – CH – CH2              
                                     |         |                            |                    |
                                   NH2   NH2                        NH2                 NH2
                                1,2-diaminopropane        1,3-diaminopropane

     Here we see that only the ligands are exchanged their position in order to show ligand isomerism.

7. Polymerization isomerism:


  • Polymers are not real isomers.
  • These type of isomers have same emperical formula but different molecular formula.
  • All these isomers have same ratio of metal atoms and ligands in them.
  • Coordintion polymers of Pt2 ion:
    Complex compound
    Number of  Pt2+
    Number of  NH3
    Number of  Cl-
    Ratio
    [Pt(NH3)2Cl2
    1
    2
    2
     1:2:2                 
    [Pt(NH3)4][PtCl4]
    2
    4
    4
    [Pt(NH3)4][Pt(NH3)Cl3]2
    3
    6
    6
    [Pt(NH3)3Cl]2[PtCl4]
    3
    6
    6

Friday, 16 November 2018

Isomerism in coordination compound

  •  Compound having same chemical formula but different arrangement in their constituent atoms are called isomers.
  • Due to the complicated formula of many coordination compound, their is a possibility of different types of bond and number of shapes, so different types of isomerism may occur. 
  • Since their atoms are arranged differently, therefore, isomers have different physical and chemical properties(colour, melting point, boiling point and solubility) with different reactivity also.
  • Coordination compound exhibit the same types of isomer as organic compound.
  • Isomers are mainly classified into two types i.e.
               1. Structural isomerism
               2. Stereo isomerism
  • Structural isomerism is further classified into seven types i.e.
               1. Ionisation isomerism
               2. Hydrate isomerism
               3. Linkage isomerism
               4. Coordination isomerism
               5. Coordination position isomerism
               6. Ligand isomerism
               7. Polymerization isomerism
  • And stereo isomerism is classified into two types i.e.
               1. Geometrical isomerism
                2. Optical isomerism
      I will update in detail about this topic in my next article. 

Thursday, 15 November 2018

Concept of free energy

  • Free energy is a thermodynamic function like enthalpy and entropy.
  • It is also known as free enthalpy.
  • Free energy is used to determine the changes made by a system and how much work it produced.
  • It is expressed in two forms i.e. (1) Helmholtz free energy
                                                             (2) Gibb's free energy

Gibbs free energy:

  • It is named in honor of the great American physicist J.W. Gibb's(1839-1903).
  • Gibb's free energy(G) is used to calculate the maximum reversible work done of a thermodynamic system at constant temperature and pressure.
  • Or this is the maximum amount of non expansion work, that can be extracted from a  completely reversible closed system .
  • Gibb's free energy also tells weather the process is spontaneous or not, i.e.if the change in free energy is negative the process is spontaneous, and if positive the process is non spontaneous.
  • Mathematically
             G = H - TS
         => ∆G = ∆H - T∆S
            Where ∆G = change in Gibb's free energy
                          ∆H = change in enthalpy
                          ∆S = change in entropy

Helmholtz free energy:

  • It is named in the honor of German physicist Hermann von Helmholtz(1821-1894).
  • It is also termed as Work function or Helmholtz function ( A) 
  • It is a type of thermodynamic potential that measures the useful work obtained from a closed system at constant temperature and volume.
  • If the change in Helmholtz free energy is negative, that means maximum amount of work is performed by a system at constant volume.
  • And if the volume is not constant the part of this work is performed as boundary work.
  • Mathematically, A = U - TS
                        =>∆A = ∆U - T∆S

Wednesday, 14 November 2018

Evidence in favour of WERNER'S THEORY

1. Electrical Conductance Measurement:

  • Molar conductance of a substance depends upon the number of charges on the particle produced by the substance.
  • As the number of the particle (i.e. ions) and charges on the coordination sphere increases, molar conductance of the compound increases.
  • For example molar conductance for aqueous solution of cobalt(III)chloride complexes with ammonia decreases in the order,
                                      [Co(NH3)6]Cl3 > [Co(NH3)5Cl]Cl2  > [Co(NH3)4Cl2]Cl  > [Co(NH3)3Cl3]
number of particle/ions             4                            3                             2                         1
                          charge             -3                           -2                           -1                         0
           1.[Co(NH3)6]Cl3 →  [Co(NH3)6]3+ + 3Cl-
           2.[Co(NH3)5Cl]Cl2  → [Co(NH3)5Cl]2+ + 2Cl-
           3.[Co(NH3)4Cl2]Cl→ [Co(NH3)5Cl]++ Cl-
            4.[Co(NH3)3Cl3]
      If we notice 1st equation, it is clear that  [Co(NH3)6]Cldissociates to give 4 particles i.e.one  [Co(NH3)6]3+ ion and three Cl-  ion And charge on the coordination sphere is -3.
So if we consider all the above equation, we will notice that there is a decreasing order in the number of particle and charges, on the coordination sphere from top to bottom. Therefore molar conductance decreases from top to bottom.

2.Cryoscopic Measurement:

  • The cryoscopic measurement means, measurement of depression in freezing point.
  • The depression in freezing point is a colligative property and depends upon the number of particles in the solution. Greater the number of particle more will be the depression in freezing point.
  • If a species dissociates into two, three, four.......ions, then depression in freezing point will be two, three, four ....... times respectively.
  • Thus the cryoscopic measurement gives the number of ions produced by the dissociation of an ionic compound.

3.Precipitation Reaction:

  • The number of ions furnished by a coordination compound can also be determined by precipitation reactions.
  • When the complexes CoCl3.6NH3,CoCl3.5NH3 ,CoCl3.4NH3 are treated with excess of AgNO3 solution, the number of chloride ion precipitated as AgCl is 3, 2, 1 respectively. This indicate that number of chloride ion in ionization sphere is 3, 2 and 1 respectively. The reactions are given below ,

           CoCl3.6NH3 +3 AgNO3 → 3AgCl + [Co(NH3)6](NO3)3
          CoCl3.5NH3 + 2AgNO3 → 2AgCl + [Co(NH3)5Cl](NO3)2

          CoCl3.4NH3 + AgNO3 → AgCl + [Co(NH3)4Cl2](NO3)

  • The structure provided by precipitation reactions are similar to those given by Werner.
  • The complex gives no precipitate with the solution. This indicates that all the three chloride ion are present in the coordination sphere in this compound.

Tuesday, 13 November 2018

WERNER'S THEORY

  • In 1893 Werner produced a theory of coordination compound to explain the structure  and formation of compound.
  • Werner was the first inorganic chemist to be awarded Nobel prize for chemistry in1913
  • Werner postulated that metal exhibits two type of valancies i.e. 
                                          (1)Primary valancy and 
                                          (2)Secondary valancy 

Primary valency:

  • The ligands which satisfy primary valency always ionic in nature.
  • Primary valency is ionizable and non directional.
  • Primary valency only satisfied by negative ions i.e. anions and are written outside the coordination sphere.
  • Primary valency donot decide geometry of the coordination compound.
  • Primary valency corresponds to the oxidation state of the metal ion.
  • Primary valency is represented by dotted line i.e.(..........)

Secondary valency:

  • The ligands which satisfy secondary valency always covalent in nature.
  • Secondary valency is non ionizable and directional.
  • Secondary valency is satisfied by either neutral or negative or both type of ligands.
  • Secondary valency decide geometry of the complex 
  • Secondary valency corresponds to the coordination number of the metal ion.
  • Secondary valency is represented by solid line.

Question for you:

      In [Co(NH3)4Cl2]Cl   chlorine ligand satisfies which type of valency.

  

Sunday, 11 November 2018

Coordination compound

Definition of Coordination compound:

  • Ligand : Any species(ion or molecule) that have at least one lone pair of electron and can donate its lone pair of electron to a metal cation or atom is called a ligand. Since a ligand is an electron rich species it is also called Lewis base or nucleophile.
  • A metal cation is an electron deficient species and can accept a lone pair of electron, there fore it act as a Lewis acid or electrophile.
  • When a group of ligand donate its lone pair of electron to the metal cation or atom coordinate bonds are formed and the product formed is called a coordination compound
  • Thus the compound in which metal cation or atom is attached to a group of ligand by coordinate bond is called a coordination compound.
  • Or a complex ion in which a metal cation is attached to the ligand by coordinate bonds.

Structural formula of Coordination compound:

  • Here the central metal cation or atom and the ligand attached to it are written in a square bracket i.e.[ ] which is called coordination sphere.
  • The cation or anion outside the coordination sphere is called the ionization sphere or counter ion.
  • The atom in a ligand that is directly attached to a metal cation or atom is called the donor atom and the number of donor atom attached to a metal cation or atom is called the coordination number .
  • For example ,coordination number of   Ag+ in [Ag(NH3)2]2+   is 2
                                                                                 Cu+ in [Cu(NH3)4]2+ is 4

                                                                                 Co3+in [Co(NH3)6]3+  is 6

Properties of Coordination compound;

  • The coordination compound may be either neutral molecule or ionic compounds. In ionic coordination compound either the cation or anion or both may be complex ion.
  • The coordination compound retain their identity more or less even in solution though partial dissociation may occur.
  • These compound do not give the tests  of  all their constituent ion in aqueous solution i.e. some constituent ion lost their identity in aqueous solution. For example  [Co(NH3)6]Cl3 is a complex compound  and it does not give the test of all the constituent ions, Co3+and Cl-  instead it gives the    Co3+ as  [Co(NH3)6]3+ complex ion and  Clion.

Saturday, 10 November 2018

Le-Chatelier's principle

Le-Chatelier's principle:

  • This is based on the fundamental of a stable equilibrium.
  • It states,when a system at equilibrium is subjected to a change in temperature,pressure or concentration of a reacting species,the system react in a way that partially offset the change while reaching a new state of equilibrium.

Effect of concentration:

If the concentration of a reacting component is increased,reaction shifts in a direction which tends to decrease its concentration.e.g. in the following example.

N2(g) + 3H2(g)  2NH3
[reactant] ↑         foreward shift
[product] ↑          backward shift
  • If the concentration of reactant is increased at equilibrium then reaction shifts in the foreward direction.
  • If concentration of product is increased then reaction shifts in backward direction.
Note: The addition of any solid component doesnot effect the concentration. 

Effect of volume:

  • If volume is increased,pressure decreases hence reaction will shift in the direction in which pressure increases that is in the direction in which number of moles of gases increases and vice versa.
  • If volume is increased then for,
          1. ∆ng > 0 ,reaction will shift in the foreward direction 
                PCl5(g)  PCl3(g) + Cl2(g)  , ∆ng = 2-1 =1 

          2. ∆ng < 0 ,reaction will shift in the backward direction
                 N2(g) + 3H2(g) = 2NH3(g)  , ∆ng =2-4= -2 < 0

          3. ∆ng= 0 ,reaction will not shift e.g.
              H2(g) + I2(g)   2HI(g)  (no effect)

Effect of pressure:

  • On increasing pressure,equilibrium will shift in the direction in which pressure decreases,i.e. number of moles in the reaction decreases and vice versa.
  • Pressure is directly proportional to number of moles.
           1. For ∆ng= 0 ,no effect
           2. For  ∆ng > 0
               If pressure decreases equilibrium shifts to forward direction.
               If pressure increases equilibrium shifts to backward direction.
           3.For  ∆ng < 0
               If pressure  increases equilibrium shifts to forward direction.
               If pressure decreases equilibrium shifts to backward direction.

Effect of catalyst:

  • Due to catalyst ,state of equilibrium is not affected i.e.no shift will occur as catalyst lowers the activation energy of both the forward and reverse reaction by same amount.
  • Thus alternating the forward and reverse rate equally and hence, the equilibrium will be attained faster i.e.time taken to reach the equilibrium is less.

Effect of inert gas addition:

  • at constant volume: Inert gas addition has no effect at constant volume  
  • at constant pressure: If inert gas is added at constant pressure,volume is increased and hence equilibrium will shift in that direction in which larger number of gaseous moles are formed.
           1.∆ng > 0 , reaction will shift in forward direction.
           2.∆ng < 0 , reaction will shift in backward direction.
           3.∆ng= 0 ,  no effect

Effect of temoerature:

  • :Exothermic reaction:The reaction in which heat is evolved.
            1.If temperature increases equilibrium will shift in backward direction.
            2.If temperature decreases equilibrium will shift in forward direction.
  • Endothermic reaction: The reaction in which heat is consumed
           1.If  temperature increases equilibrium will shift in forward direction.
           2..If  temperature decreases equilibrium will shift in backward direction.

Friday, 9 November 2018

Thermodynamics of equilibrium

Reaction Quotient(Q):

         At each point in a reaction ,we can formulate a ratio of concentration terms having the same form as the equilibrium constant expression. This ratio is called the reaction quotient denoted by symbol Q.
It helps in predicting the direction of a reaction.

For a general reaction:

     aA(g) + bB(g) ⇔ cC(g) + dD(g) 

      Q=[C]tc[D]td/ [A]ta[B]tb

  1. If the net reaction is at equilibrium,Q= Kc
  2. A the net reaction proceeding from right to left(the reverse direction) if  ,Q > Kc

Thermodynamics of equilibrium:

     For a general reaction, mA + nB ⇔ pC + qD 


∆G =∆G⁰ + 2.303RTlog10Q


Where,    ∆G   = Gibb's free energy change.
                ∆G⁰ = Standart Gibb's free energy change.
                Q     =  Reaction quotient.
 Since at equilibrium,Q=K
 Here K is the thermodynamic equilibrium constant replacing  Kc or  Kp 
 K=(aC)p(aD)q/(aA)m(aB)   
Here aX   denotes the activity of x.
In fact,is the ratio of activity of substance at equilibrium and its activity in standard condition.That is why it is unitless and K is also unitless. 

Note:

  1. Thermodynamics equilibrium constant is unitless since activity is unitless.
  2. For pure solids and pure liquids activityis unity.
  3. For gases (ideal behavior),the activity is partial pressure(in atm)
  4. For components in solution, activity is molar concentration
  5. For endothermic reaction()value of equilibrium constant increases with the rise in temperature.
  6. For exothermic reaction, value of equilibrium constant decreases with increase in temperature.

Condition of spontaneity: 

  •    ∆G<0 for a spontaneous process or reaction.                 
             Since, ∆G = ∆H - T∆S
                   = > ∆H - T∆S < 0
                   = >  T >  ∆H/T∆S
  • ∆G > 0 for a non spontaneous process or reaction
  • ∆G = 0 for a equilibrium reaction

Wednesday, 7 November 2018

Important relationship involving equilibrium constant

1. If we reverse an equation  KP or  KC  is reversed.
           If              A + B ⇔ C + D         KC = 10  
           then for    C + D A + B          K= 10-1
2. If we multiply each of the coefficient in a balanced equation by a factor n,then equilibrium constant is raised to the same factor.
    ½ N2 + ½O2 ⇔ NO            KC = 5
              N2  +  O2 ⇔ 2NO               KC = 52 = 25 
 3. If we divide each of the coefficients in a balanced equation by a factor n, then new equilibrium constant is the nth root of the previous value.
          2SO2 + O2      2SO3              KC =25
          SO2 + 1/2 O2   SO3B     KC = (25)1/2

4. When we combine individual equation, we have to multiply their equilibrium constant for net reaction.
           If K1 , K2 and K are stepwise equilibrium constant for  A⇔B , B⇔C , C⇔D   .
          Then for A⇔D , the equilibrium constant is K= K1K2K
 

Significance of the magnitude of equilibrium constant:

  1. If a large value of KP or  KC signifies that the forward reaction goes to completion or very nearly so.
  2. A large value of KP or KC signifies that the forward reaction doesn't occur to any significant extent.
  3. A reaction is most likely to reach a state of equilibrium in which both reactant and product are present if the numerical value of KP or  KC is neither very large nor very small

Units of the equilibrium constant:

           For the sake of simplicity in the units of Kc or Kp the relative molarity of pressure of reactants and products are used with respect to standard condition. (For solution standard state 1 mol/liter and for gas standard pressure=1 atm).Now resulting equilibrium constant becomes unitless by using relative molarity and pressure. But the numerical value may change in the value of standard states molarity and pressure.

Sunday, 4 November 2018

Relationship between Kp ,Kc, Kx and Kn

  • Kp=Equilibrium constant in terms of partial pressure.
  • Kc=Equilibrium constant in terms of concentration.
  • Kx=Equilibrium constant in terms of  mole fraction.
  • Kn=Equilibrium constant in terms of  number of moles.
  •  Kp and Kc are related as  KP = KC (RT)∆n ...........................(eq 1)

        Relationship between KP and Kn

            ...........................(eq 2)                                 
        From ideal gas equation,PV=nRT
                                     =>P=n(RT/V)
        Where, n is the number of moles

        So,  PA =nA(RT/v), PB = nB(RT/V), PC =nC(RT/V) and PD =nD(RT/V)
     
        Replacing equation 2 by the above value we get that,     
                 [nC(RT/V)]c  . [nD(RT/V)]d 
     K=  -------------------------------------     
                 [nA(RT/V)]a  . [nB(RT/V)]b
                       nCc . nDd
    = > Kp =  -------------- .  ( RT/V ) (c + d) – (a + b)
                       nAa. nBb  
    = >  Kp = Kn . (RT/V) ∆n

    = >  Kp = Kn . (PT/nT) ∆n                                   

             ∆n=number of gaseous moles of product – number of gaseous moles of reactant

    Relation between  Kp and Kx

           From  above (eq 2)   
                                                         
          Partial pressure(P) = Mole fraction(x) . Total pressure(PT)
          So,   PA =  xA .  PT
                  PB =  xB .  P
                      PC =  xC .  PT
                      PD =  xD .  PT

        Putting the values in whole equation:
                           ( xC .  P)c . ( xD .  PT )d
                 K= ---------------------------------
                           ( xA .  PT )a . ( xB .  PT )b

                             xCc .  xDd
                       =  --------------   PT(c+d) - (a+b)
                             xAa .  xBb

            = >     KP  = Kx  (PT) ∆n 

Q.Check your understanding.
   
      N2O4(g)=2NO2(g) ,Calculate Kand Kfor the given reaction for which Kp=0.157