Thermo Chemistry Beauty

*Thermochemistry* 

* Thermochemistry is the study of the thermodynamics of chemical reactions.

* Enthalpy : Heat content of a system

* Endothermic reaction : The enthalpy change that occurs when heat is absorbed by a system. ∆H= +ve i.e change in enthalpy for this reaction is always positive.

* Exothermic reaction: The enthalpy change that occurs when heat is given off to the surroundings from a system. ∆H=-ve i.e enthalpy change is always negative.

* Entropy: Degree of disorderliness in a system

* W= P∆V

W is work done by a system (S.I unit is Joules)

P is pressure in atm

V is volume in Litres

*  Increasing Endothermic change

--------------------------------------->

   Solid --> Liquid --> Gas

<--------------------------------------

    Increasing Exothermic          change

i.e, Solid ---> liquid is Endothermic

      Liquid ---> Gas is also Endothermic

But, 

      Gas ---> liquid is Exothermic

     Liquid ---> Solid is also Exothermic

*Reversing a thermochemical equation changes the enthalpy sign. 

i.e, 

N2 + 3H2 ---> 2NH3, ∆H= -ve

2NH3 ---> N2 + 3H2, ∆H=+ve.

* Q=mc0

Q is quantity of heat

m is mass

c is specific heat capacity

0 is temperature difference (0²-0¹)

* Q= mL

L is latent heat

This occurs when there's a change of phase.

* C of H2O is 4.2KJkg-¹°C-¹

(Specific heat capacity of water)