# Chemistry

posted by .

Write a balanced equilibrium equation and kb expression for the reaction of the hydrogen phosphate ion (HPO4^2-) with water.

Answer: HPO4^2-(aq) +H2O(l) <--> PO4^3-(aq) +H3O+ (aq)

kb= [PO4^3-][H3O+]/ [HPO4^2-]

is that right?

• Chemistry -

No. You wrote the equilibrium for Ka for HPO4^2-. You donated a proton which makes it an acid. You want it to accept a proton.
HPO4^2- + HOH ==> H2PO4^-

• Chemistry -

So, the balance equation would be: HPO4^2- + H2O -> H2PO4 + H3O+?

and the kb would be: [H2PO4][H3O]/[HPO4^2-]

is that right?

• Chemistry -

Yes. That's the Kb expression; the value of Kb, which is not in the question but comes in handy when calculating pH of salts etc is Kb = (Kw/k2 for H3PO4)

## Similar Questions

1. ### acid base chem

I'm reviewing my notes for a test tomorrow, and I found that I have a question concerning acids that under go multiple protonizations. I know the molarity [or moles, if that's being calculated] of H3O+ of the first protonization can …
2. ### chemistry

AlPO4(s)<=>Al^3+(aq)+PO4^3-(aq) PO4^3-(aq)+H3O^+(aq)<=>HPO4^2-(aq)+H2O(l) What is the net ionic equation for AlPO4(s) dissolving in H3O^+(aq)?
3. ### Biochemistry DR.BOB

How many grams of NaOH(Mr 40) must be added to 100 ml of 0.1M H3PO4 to create phosphate buffer, pH 7.0?
4. ### Chemistry

Which of the following can be amphoteric?
5. ### Chemistry- HW Check

I have seven homework problems. I did them but I wasn't sure if I did them correctly. Did I do them correct?
6. ### chem: Drbob222

Hi I have a follow up to a question that was answered previously. New question: So when the HPO4(2-) reacts with the NaOH, will the equation be this?