Help with Chemistry just give me any advice you can for this problem or resources?

[aslan649]

Did a lab in class with Phosphoric Acid (H3PO4) well this has 3 dissociations as it goes from H3PO4 to H2PO4 to HPO4. I need to get the pH of this reaction and I've recieved each of the Ka's ranging from 6.92x10^-3 6.17x10^-8 and 2.09x10^-12. Does that mean I would have to find the pH at each of these levels? Then it asks me to find the moles broken/formed with Phosphoric Acid and Sodium Hydroxide... How would I go about doing that? Is it just the last reaction combining with NaOH? The first of H3PO4? Any help would be greatly appreciated list any resources or any information that may help me thanks a million.