Determination of Ph of strong and weak acids

Determination of Ph

Strong acid: the acid which is completely dissociates into ions

Strong acids examples: HCl, H2SO4, HNO3

because of complete dissociation the concentration of [H+] equals the concentration of the acid it self  so to determine the ph it equals : Ph= -log[H+]

In Weak acids:

weak acids partially dissociate into ions then the concentration of H+ is not equal to concentration of acid it self ,but we have to determine it 

then the [H+]= √ka Ca

Ka is dissociation constant of acid and Ca is concentration of acid {this relation is derived by Ostwalds}

the Ph of weak acid is the same as strong one : Ph= -[H+]

  

Electrochemical series

Any oxidation reduction reaction 

follow the series

This series arrange the elements according to their oxidizing and reducing ability:

the lower elements can replace the higher one in the solution, for instance:

 As shown in the pic. the zinc when placed in copper sulfate it replaces the copper ions by reducing it  while zinc it self is oxidized   

but, if we put a copper piece in zinc solution no chemical reaction occurs this is due to the zinc has higher reducing agent than copper

as previous also if we immerse an iorn in zinc solution nothing will occur due to zinc is higher reducing agent than copper