[vijay_cluster]

The pH of solution prepared by mixing 100ml  O.1M Na3PO4 and 200ml   O.1M HCl ? ( For H3PO4   Pka1  = 3 ,  Pka2 = 7  and  PKa3= 10 ) 
 
The answer is given as PH =5.


I am not getting how to solve this problem i tried this by finding H+ conc. by multiplying ka values. please help me to solve this problem

[Borek]

There are reactions taking place in this mixture, can you write them?

[utkuarslan]

Hi vijay_cluster!

Firstly write reaction. Na3PO4 + HCl -> Na2HPO4 + NaCl
Similarly as write the second reaction. In the meantime, You should control the number of moles of entrants and products. Number of moles of HCl in which step ends, by the step created Ka equation. Of course, you gotta watch your reactions to the use of Ka or Kb.The rest is owned by calculator.