Question

Calculate the ph of 5×10^-3 M of H2SO4

Answer 1

H2SO4 will dissociate as follows:
H2SO4-----2H+ + SO4--
Since H2SO4 is a strong electrolyte, it will furnish twice as many ions in its aqueous solution as the number of molecules.Therefore the concetration of H+ ions will be double the concentration of H+ ions.Therefore H+ ion concentration is 2x5x10-3 that is 10x10-3=10-2.Now pH = -Log[H+].Therefore pH= -Log10-2=-(-2)=+2.
Therefore pH is +2

Answer 2

I know that H2SO4 is a polyprotic acid 

I am given that Ka 1 = large and Ka 2 = 1.2 e -2 

after that I am lost...Please help. 
A step-by-step procedure would be helpful