BORN HABER CYCLE AND ITS APPLICATIONS
Name -
Chirantan mondal
COURSE -
GENERAL CHEMISTRY
COURSE CODE-
BBTC303
Degree -
Bachelor of Science (Honors) in Biotechnology
Semester -
3rd semester
Roll No. -
19010310011
Registration No. -
19013000357
HISTORY AND INTRODUCTION
➢ The Born–Haber cycle is a method of analyzing reaction energy. Two
German scientists Fritz Haber and Max Born developed it in the year 1919
and it was therefore named after them.
➢ It explains and helps in understanding the formation of ionic compounds. It
is primarily used to calculate lattice energy as it cannot be measured directly.
➢ Hess’s Law states that when a reactant is converted to a product, then the
change in enthalpy is the same irrespective of the reaction taking place in
one step or series of steps. Born Haber Cycle uses Hess’s law to calculate
lattice enthalpy.
➢ Lattice energy is defined as the energy required to separate a mole of an
ionic solid into gaseous ions.
LATTICE ENTHALPY DEFINITION(S)
1. Lattice Formation Enthalpy
‘The enthalpy change when ONE MOLE of an ionic lattice is formed from its
isolated gaseous ions.’
Values
Example
highly EXOTHERMIC
strong electrostatic attraction between oppositely charged ions
a lot of energy is released as the bond is formed
relative values are governed by the charge density of the ions.
Na+(g)
+
Na+ Cl¯(s)
Cl¯(g)
2. Lattice Dissociation Enthalpy
‘The enthalpy change when ONE MOLE of an ionic lattice dissociates into
isolated gaseous ions.’
Values
Example
Na+(g) + Cl–(g)
NaCl(s)
Na+(g) + Cl–(g)
highly ENDOTHERMIC
strong electrostatic attraction between oppositely charged ions
a lot of energy must be put in to overcome the attraction
relative values are governed by the charge density of the ions.
Na+ Cl¯(s)
Na+(g)
+
Cl¯(g)
NaCl(s)
BORN LANDE EQUATION
➢ The Born-Lande equation is a concept originally formulated in
1918 by the scientists Max Born and Alfred Lande and is used
to calculate the lattice energy.
➢ The disadvantage of Born-Lande included the use of Madelung
constant is that these equations can be applied only to crystals
of which lattice type is certain.
NA = Avogadro constant;
M = Madelung constant, relating to the
geometry of the crystal;
z+ = numeric charge number of cation
z− = numeric charge number of anion
e = elementary charge, 1.6022×10−19 C
ε0 = permittivity of free space
4πε0 = 1.112×10−10 C2/(J·m)
r0 = distance to closest ion
n = Born exponent, typically
a number
between 5 and 12, determined
experimentally
by
measuring
the
compressibility of the solid, or derived
theoretically.
ENERGETICS OF BORN HABER CYCLE
1. IONIZATION ENERGY: The energy required to take o an electron from the neutral ion/atom. In order to do this,
there should be an input of energy, which is why it is always positive. Ionization energy is noted to be increasing
across the periodic table from left to right, and decreasing from top to bottom.
For example: Ionization of gaseous sodium atom to give sodium ion.
Na(g)
Na+(g) + eˉ ;
H= 493.8 kJ molˉ¹
2. ELECTRON AFFINITY: The energy released when an electron is added to a neutral ion/atom. The energy
released is known to have a negative value, but due to the definition of affinity, it is denoted as a positive value. The
electron affinity is known for increasing from left to right and decreasing from top to bottom in a periodic table.
For example: Conversion of gaseous chlorine atom to chloride ion (addition of electron).
Cl(g) + eˉ
Clˉ (g) ;
H = –379.5 kJ molˉ¹
ENERGETICS OF BORN HABER CYCLE
3. DISSOCIATION ENERGY: The energy needed to break a compound apart. Dissociation is an endothermic process
that requires an input of energy. Therefore, its value is always positive. The magnitude of it is dependent on the
electronegativity of the atoms involved in the compound.
For example: Dissociation of gaseous chlorine molecule into chlorine atoms.
½Cl2(g)
Cl(g) ;
H = –120.9 kJ molˉ¹
4. SUBLIMATION ENERGY: Known as the energy of atomization, it is required to turn the compound from solid to
gas while passing through the liquid phase. It is again an input of energy and is always positive.
For example: Sublimation of solid sodium to gaseous sodium atoms.
Na(s)
Na(g);
H=108.7KJmolˉ¹
5. THE HEAT OF FORMATION: It is the change in energy when a particular compound is formed from elements. It
can be either positive or negative based on the atoms involved and their interaction.
EQUATION OF BORN HABER CYCLE
BORN-HABER CYCLE GENERAL FORMAT FOR ANY MX IONIC COMPOUND
Hfº =
Hsub+ 1st IE +2nd IE +
Hdiss +1st EA+ 2nd EA –LE(U)
Hfº = Enthalpy of formation
Hsub =Enthalpy of sublimation
M(s)
+
Hfº
½X2(g)
Hsublimation
MX(s)
Hdissociation
1st IE = First Ionization energy
2nd IE = Second Ionization energy
Hdiss = Enthalpy of dissociation
1st EA = First Electron affinity
2nd EA = Second Electron affinity
LE(U) = Lattice energy
M(g)
X(g)
IONIZATION
ENERGY (IE)
M+(g)
ELECTRON
AFFINITY (EA)
+
X–(g)
LATTICE
ENERGY
(U)
BORN HABER CYCLE OF NaCl
Enthalpy of formation of NaCl
Na(s) + ½Cl2(g) ——>
NaCl(s) ;
Hfº =- 411.3(KJ /mol)
Na(s)
+
½Cl2(g)
Hfº
NaCl(s)
Enthalpy of sublimation of sodium
Na(s)
——>
Na(g) ;
Hsub = + 108.70 (KJ /mol)
Enthalpy of dissociation of chlorine
½Cl2(g) ——>
Cl(g) ;
Na(g)
Hdiss =+ 122.0 (KJ /mol)
Cl(g)
Ist Ionisation Energy of sodium
Na(g) ——> Na+(g) + e¯ ; 1st IE =+ 495.0(KJ /mol)
Electron Affinity of chlorine
Cl(g) + e¯
——>
Na+(g)
+
Cl–(g)
Cl¯(g) ; 1st EA =- 349.0(KJ /mol)
Lattice Enthalpy of NaCl
Na+(g) + Cl¯(g) ——> NaCl(s) ; LE(U)
=?
Calculate the lattice enthalpy for NaCl, from given the information:
-411.3=+108.70+122.0+495.0-349.0-LE ;
Hfº =
OR, LE = -788.0 KJ/ mol .
Hsub +
Hdiss + 1st IE+ 1st EA- LE
Lattice energy for NaCl = 788.0 KJ/mol
APPLICATIONS OF BORN HABER CYCLE
➢ Born-Haber cycle is used to calculate the lattice energy which cannot be measured directly otherwise.
➢ It is also used to determine electron gain enthalpy and ionization energy.
➢ It can also be used to explain the stability of molecules. e.g -The net effect is that the enthalpy change
of formation of MgCl2 is more negative than that of MgCl, meaning that MgCl2 is the more stable.
➢ Helps us to justify the formula of ionic compound that are written.
ACKNOWLEDGEMENT
I would like to express my special thanks of gratitude to my teacher Dr. Arpita Sarkar and Prof. Anirban Bhar
Sir, who gave me the golden opportunity to do this wonderful project of General chemistry “Born haber cycle
and its applications”
Who also helped me in completing my project.
I came to know about so many new things I am really thankful to him.
Secondly I would also like to thanks my parents and friends who helped me a lot in finalizing this project within
the limited time frame.
THANK YOU