# AP CHEMISTRY

Phosphoric acid is triprotic acid (three ionizable hydrogens). The values of its stepwise ionization constants are Ka1= 7.5E-5, Ka2= 6.2E-8, and Ka3= 4.2E-13

1) Write the chemical equation for the first ionization reaction of phosphoric acid with water

2)Write the equilibrium constant expression (Ka1) for this reaction.

3)What would be the pH of a solution when [H3PO4]= [H2PO4-]?
(Note: pH= -log[H3O+])

1. 👍
2. 👎
3. 👁
4. ℹ️
5. 🚩
1. What is your trouble with this? What do you not understand?

1. 👍
2. 👎
3. ℹ️
4. 🚩
2. I don't understand how to do the first one.
I really don't know how to do reactions

1. 👍
2. 👎
3. ℹ️
4. 🚩
3. You know acid + water ionizes to give H3O^+ so take the H3O^+ out and see what's left.
H3PO4 + H2O ==> H3O^+ + H2PO4^-
Then Ka1 = (H^+)(H2PO4^-)/(H3PO4)

For the pH.
The pH when (H2PO4^-) = (H3PO4). Note one is in the numerator, the other is in the denominator, they cancel and you are left with Ka1 = (H^+), convert that to pH.

1. 👍
2. 👎
3. ℹ️
4. 🚩
4. thanx very much!!!!!

1. 👍
2. 👎
3. ℹ️
4. 🚩
5. You're welcome. It helps us if you DON'T change screen names.

1. 👍
2. 👎
3. ℹ️
4. 🚩

## Similar Questions

1. ### Chemistry

Phosphoric acid, H3PO4(aq), is a triprotic acid, meaning that one molecule of the acid has three acidic protons. Estimate the pH, and the concentrations of all species in a 0.300 M phosphoric acid solution. pKa1: 2.16 pKa2: 7.21

2. ### chem

Arsenic acid (H3AsO4) is a triprotic acid with Ka1 = 5 10-3, Ka2 = 8 10-8, and Ka3 = 6 10-10. Calculate [H+], [OH -], [H3AsO4], [H2AsO4-], [HAsO42-], and [AsO43-] in a 0.20 M arsenic acid solution. i cant do this. i don't even

3. ### Chemistry

Phosphoric acid, H3PO4(aq), is a triprotic acid, meaning that one molecule of the acid has three acidic protons. Estimate the pH, and the concentrations of all species in a 0.300 M phosphoric acid solution. kPa1: 2.16 kPa2: 7.21

4. ### Analytical Chemistry

Phosphoric acid is a triprotic acid with the following pKa values: pka1: 2.148 pka2: 7.198 pka3: 12.375 You wish to prepare 1.000 L of a 0.0100 M phosphate buffer at pH 7.45. To do this, you choose to use mix the two salt forms

1. ### chemistry

A 0.185 M solution of a monoprotic acid has a percent ionization of 1.55%. Determine the acid ionization constant (Ka) for the acid.

2. ### Chemistry

Calculate the percent ionization of nitrous acid in a solution that is 0.311 M in nitrous acid (HNO2) and 0.189 M in potassium nitrite (KNO2). The acid dissociation constant of nitrous acid is 4.50 × 10-4.

3. ### chemistry

Calculate the molarity of a phosphoric acid(H3PO3)solution that is 84% by mass phosphoric acid and has a density of 1.87g/mL.?

4. ### Chemistry

How do I prepare 10% ortho-phosphoric acid in 250ml volumetric flask from 85% ortho-phosphoric acid(density 1.69g/ml) ?

1. ### Chemistry

The triprotic acid H3A has ionization constants of Ka1 = 6.8× 10–3, Ka2 = 8.1× 10–9, and Ka3 = 5.0× 10–12. Calculate the following values for a 0.0760 M solution of NaH2A [H+] = ? [H2A-]/[H3A]= ? Calculate the following

2. ### chemistry

Phosphoric acid is a triprotic acid with pKa's of 2.14, 6.86, and 12.4.The ionic form that predominates at pH 3.2 is?choose the corect answer (a) H3PO4 (b) H2PO4^- (c) HPO4^2- (d) PO4^3-

3. ### Chem 2

A 0.15 M solution of butanoic acid, C3H7COOH, has a pH of 2.8210. Find the Ka of butanoic acid. Call buanoic acid HB. Then the ionization is HB ==> H^+ + B^- To start (HB) = 0.15 (H^+) = 0 and (B^-) = 0 After ionization, (H^+) = x

4. ### chemistry, science

Phosphoric acid is a triprotic acid: H3PO4(aq) +H2O(l) ↔ H3O+(aq) + H2PO4-(aq) Ka1 = 7.5 x 10-3 H2PO4-(aq) +H2O(l) ↔ H3O+(aq) + HPO42-(aq) Ka2 = 6.2 x 10-8 HPO42-(aq) +H2O(l) ↔ H3O+(aq) + PO43-(aq) Ka3 = 4.8 x 10-13