Different kind of enthalpy/ heat changes.

  change of heat in a reaction is the change in enthaply, the energy evolved or consumed obviously in a reaction is termed as enthalpy change in modern chemistry  .

Sublimation enthalpy/ Heat of sublimation.

The energy consumed by one mole of solid substance to convert directly from solid to gaseous state is known as sublimation enthalpy.

Its a one step process if we make it 2  then there   may  be a  change in enthalpy will happen, And is considered as wrong. 

 

Sublimation reaction is a endothermic reaction as there is the consumption of  heat energy . 

     C (s)   ➡  C (g)     🔺H=+717.02kj/mol

Here sublimation enthalpy of C is 717.02kj/mol. 

Ionisation enthalpy/ heat of  ionisation

In gaseous state the energy consumed by one mole of any  nutral substance to convert it into one mole of positively charged ion  is known as  ionisation energy.

 I.e  the energy consumption for   bring out the   outermost orbital electron from a nutral substance.  Is also an endothermic process  enthalpy change is positive . 

Na  ➡  Na+  +   e–    🔺H= 494kj/mol

Atomization energy/Atomization enthalpy

 The amount of energy consumed by one mole of any substance to convert it into gaseous atom . 

I.e  the  liquid substance consumed an amount of heat energy and the enthalpy change is the  vaporization enthalpy. 

The energy consumption by Cl in atomization is  +121kj/mol. 

 1/2   Cl2(g)  ➡  Cl (g) 

here a things to highlight   the energy  consumption  is not by one mole of Cl molecule but one mole of Cl atom. 

Vaporization enthalpy/ heat of vaporization  

 The energy consumption by one mole of any liquid substance  to convert it into  one mole of gaseous substance at 1 atm pressure . 

Liquid water consumes  +41 kj/mol in its boiling point to convert it into gaseous water vapour. 

     H2O (l)   ➡  H2O   (g)

Heat of Fusion/ Fusion enthalpy 

 The energy  required to convert a solid substance into liquid,  obviously the heat of fusion is different for different substances, also a characteristics property of any substance. 

H2O (l)    ➡    H2O(g)   🔺H=+6 kj/mol

Electron affinity / Electron affinity enthalpy. 

 The amount  of energy released for one mole of any nutral  gaseous atom  to convert it into  one mole of negatively chaged  gaseous atom, that means the addition of one mole  electron to  one mole nutral gaseus substance. 

 This  is an exothermic process. 

For example 

  Cl(g)   ➡    Cl- (g)    🔺H=-348kj/mol 

Lattice enthalpy 

 The energy evolved at the last stage of an ionic bond formation the required amount  of gaseous  ions from infinit distance to get them together  for the formation of a solid lattice. 

In other words the energy evolved  in the formation of a lattice from the isolated gaseous inagurent atoms. 

 As energy is evolved in this process the change  is exothermic and enthalpy change must be negative in value. 

 K+     +    Cl-    ➡  KCl   🔺H=-760kj/mol

 

Heat of combustion/ combustion enthalpy  

At a certain themperature and 1 atm pressure  change in enthalpy for completly burning  1 mol substance by oxygen is known as combustion enthalpy.    

And the energy evloved in burning of any  1 mol substance by oxygen at 25°c and 1 atm is known as   heat of standard combustion / standard combustion enthalpy. 

  C   +    O2     ➡   CO2     🔺H=-395kj/mol

Neutralization enthapy / heat of nutralization.  

  

At 25°c and 1 atm the heat energy evloved in a chemical reaction of an acid and a base to produce one mole of water  is known as  heat of nutralization , the enthalpy change is known as  nutralization  enthalpy 

 The nutralization reaction of HCl and NaOH to produce one mole of water  is  with evolving of 57.34 kj/mol 

 

HCl+ NaOH ➡NaCl+H2O 

🔺H=57.34kj/mol

 

Normally the nutralization of  strong acid and base occured with evolvin 57.34kj/mol.    

Heat of solution/ solution enthalpy 

At a cetain temperature if one mole of any solute is solvated into a sovent and after adding more solvent to that solution and no change in the  temprature of the solution  then the temperature change is termed as  heat of solution.  

 The heat of solution depend on the nature of the solute and solvent if there is  any reaction occured Then   enthalpy change will be positive in value  and  if no reaction occured then  enthalpy change will negative in value. 

 The hydration of CuSO4 is an example.

CuSO4 + H2O➡ CuSO4. 5H2O 

🔺H =-66kj/mol. 

 

    

Bond enthalpy/ Bond Energy  

 At gaseous state to break the bond between two  atom  of any  molecule 

i.e  the amount of energy required to break 6.02×10^23  bond between to atom of a molecule.

  M-O   ➡  M(g)   +    O(g)  🔺H=.... 

 Breaking of bond M-O causes the formation of free radical M and O. 

Read also 

 

Different method for expressing the concentration  of a solution, molarity, molality, normality, formality,  g/L,  molar fraction,w/w,  w/v,  ppm, ppb.