# chemistry

posted by .

using the following salts listed below, calculate the moles of acid and conjugate base needed to make 100 ml of 0.50 M, ph 6.5,6.7, and 6.8 phosphate buffer solution. (For H2PO4-, pka=6.64)

Salt Molar mass, g/mol
KH2PO4 136.09
NaH2PO4*H2O 137.99
Na2HPO4*7H2O 268.09
K2HPO4 174.2

• chemistry -

pH = pKa + log(base)/(acid)
You want 100 mL x 0.5M = 0.05 mols

6.5 = 6.64 + log (B/A)
Solve for B/A, then
A + B = 0.05.
Two equations and two unknowns, Solve for acid and base mols, then convert to grams from g = mols x molar mass.

I would check myself upon finishing each by substituting grams of each salt back into the HH equation and see if it givs the desired pH.

## Similar Questions

1. ### chemistry

Calculate the mass of salts needed for constructing a buffer using potassium monobasic phosphate and potassium dibasic phosphate with the total concentration of 100 mM. The solution is to be prepared in DI water and the pKa value for …
2. ### Chemistry

If a liter of a buffer is prepared with a final concentration of .3M monosodium phosphate and .5M disodium phosphate, what is the pH of this buffer?
3. ### General Chemistry

Starting out with 50 mL of 0.20 M NaHCO3, calculate how many mL of 0.50 M NaOH solution to add to make 100 mL of approximately 0.10 M (total) buffer solution with a pH of 10.35. By adding NaOH, some of the NaHCO3 gets converted to …
4. ### Chemistry

How many moles of H2PO4 and HPO4 would be needed to prepare 1.0 L of a 0.01M phosphate buffer with a pH of 6.82?
5. ### chemistry

As a technician in a large pharmaceutical research firm, you need to produce 200.mL of 1.00 M a phosphate buffer solution of pH = 7.19. The pKa of H2PO4− is 7.21. You have 2.00 L of 1.00 M KH2PO4 solution and 1.50 L of 1.00 M …
6. ### chemistry 2

You are instructed to create 800. mL of a 0.69 M phosphate buffer with a pH of 7.6. You have phosphoric acid and the sodium salts NaH2PO4, Na2HPO4, and Na3PO4 available. what is the molarity needed for the acid component of the buffer?
7. ### Chemistry

As a technician in a large pharmaceutical research firm, you need to produce 100.mL of 1.00 M a phosphate buffer solution of pH = 7.45. The pKa of H2PO4− is 7.21. You have 2.00 L of 1.00 M KH2PO4 solution and 1.50 L of 1.00 M …
8. ### college chem

You are instructed to create 400. mL of a 0.40 M phosphate buffer with a pH of 6.9. You have phosphoric acid and the sodium salts NaH2PO4, Na2HPO4, and Na3PO4 available. (Enter all numerical answers to three significant figures.) H3PO4(s) …
9. ### Chemistry

The pH of a buffer can be predicted using the Hendersen-Hasselbach equation: pH=pKa+ log([conjugate base][conjugate acid]) The choice of the conjugate acid-base pair (as you did in the previous questions) determines the pKa value to …
10. ### CHEMISTRY

As a technician in a large pharmaceutical research firm, you need to produce 450. mL of 1.00 M a phosphate buffer solution of pH = 7.20. The pKa of H2PO4− is 7.21. You have 2.00 L of 1.00 M KH2PO4 solution and 1.50 L of 1.00 …

More Similar Questions