# Chemistry

posted by .

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? (Hint: Which is conjugate acid (HA) and conjugate base (A-)? What's the pKa for this particular pair of HA and A-?)

So I think the conjugate base HA is disodium phosphate and the conjugate acid A- is monosodium phosphate. Otherwise I'm not sure where to start and I'm not sure why or how I determine that at this point.

• Chemistry -

You want to use the Henderson-Hasselbalch equation. Substitute into
pH = pKa + log[(base)/(acid)].
The base is Na2HPO4. The acid is NaH2PO4.

• Chemistry -

Okay, so based on the chart in my book I was able to determine the following.

pH=(unknown)
pKa=7.2 of Phosphoric Acid (2)
A-=.5M of Na2HPO4
HA=.3M H2PO4-
pH= 7.2 + log(.5/.3)
pH=7.2+log(1.6667)
pH=7.2+0.5108

So, the pH of this solution is:
pH=7.7108

Correct?

• Chemistry -

pH=(unknown)
pKa=7.2 of Phosphoric Acid (2)
A-=.5M of Na2HPO4
HA=.3M H2PO4-
pH= 7.2 + log(.5/.3)
pH=7.2+log(1.6667)
You are ok to here
pH=7.2+0.5108
I find 0.22 for the log of 1.6667

• Chemistry -

Upon recalculating this you are definitely correct...log(1.6667)=0.22
so 7.2+.22=7.42
and the pH is then 7.42

## Similar Questions

1. ### Chemistry

3 buffers in the human body and what are their conjugate acid-base pairs?
2. ### Chemistry

Write the chemical equation showing dihydrogen phosphate and hydrogen phosphate conjugate acid-base relationship. Identify the acid and base. Explain how the equilibrium is shifted as buffer reacts with an acid and reacts with a base.
3. ### Chemistry

Write the chemical equation showing dihydrogen phosphate and hydrogen phosphate conjugate acid-base relationship. Identify the acid and base. Explain how the equilibrium is shifted as buffer reacts with an acid and reacts with a base.
4. ### Chemistry

Write the chemical equation showing dihydrogen phosphate and hydrogen phosphate conjugate acid-base relationship. Identify the acid and base. Explain how the equilibrium is shifted as buffer reacts with an acid and reacts with a base.
5. ### chemistry

Calculate the pH of a buffer using dihydrogen phosphate and it's conjugate base. The concentration of weak acid is 0.23 M and the conjugate base concentration is 1.19 M
6. ### Chemistry

Select the statements that correctly describe buffers.?
7. ### 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 …
8. ### Chemistry

The pH of human blood needs to be between 7.35 and 7.45. You want to prepare a buffer solution that gives a pH of 7.40. You decide to use a sodium phosphate buffer: the acid is H2PO−4 and the conjugate base is HPO2− 4. …
9. ### Chemistry

c) Now make up 500 mL of a 0.025M phosphate buffer using the 0.1M phosphate buffer. Show all your workings. The 0.1M is made of 120.1ml conjugate base and 379.9ml acid.
10. ### Chemistry

c) Now make up 500 mL of a 0.025M phosphate buffer using the 0.1M phosphate buffer. Show all your workings. The 0.1M is made of 120.1ml conjugate base and 379.9ml acid.

More Similar Questions