Types of Enthalphy

• Enthalpy of Formation, ΔHf

           Heat change when 1 mole of a compound is formed from

its elements at standard condition.

          

     H2 (g) + ½ O2 (g) → H2O (l)                  H= −286 kJmol−1

 

•  Enthalpy of Combustion, ΔHcomb

            Heat released when 1 mole of substance is

burn completely in excess oxygen at standard conditions.

                
      C (s) + O (g) → CO (g)                           H= −393 kJmol−1

•  Enthalpy of Neutralisation, ΔHneut

            Heat released when 1 mole of H2O is formed from

 the neutralisation of acid and base at standard conditions.

          
   HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (aq)    H = kJmol−1

• Enthalpy of Atomisation, ΔHatom

            Heat absorbed when i mole of gaseous atom is formed

 from its element at standard conditions.

             
                 Na (s) → Na (g)                   H= 109 kJ mol−1

• Enthalpy of Sublimation, ΔHsublim

           Heat change when one mole of a substance sublimes

(solid into gas).

    
              
                I (s) → I (g)                       H= +106 kJ mol−1

• Enthalpy of Hydration, ΔHhyd

          Heat released when 1 mole of gaseous ion is hydrated in

water.

          
            Na+ (g) → Na + (aq)            H= − 406 kJ mol−1

• Enthalpy of Solution, ΔHsoln

          Heat change when 1 mole of a solute dissolves in water to

 form a very dilute solution.

          
        KCl (s) → K+ (aq) + Cl− (aq)        H= + 690 kJ mol−1