# Biochemistry

posted by .

1. MES (2-(N-Morpholino)ethanesulfonic acid) is a common buffer used in biochemistry labs to stabilize proteins. The pKa for MES is 6.09.
a. What is the pH of 1 liter of a 200 mM MES aqueous solution? Clue: you will need to solve a quadratic equation. (2.5 points)
b. How much solid NaOH (in grams) needs to be added to the MES solution to make a buffer at pH 6.5? (1.5 points)

• Biochemistry -

If we call MES just HS, then
...........HS ==> H^+ + S^-
initial....0.2.....0....0
change.....-x......x.....x
equil......0.2-x...x.....x
Substitute the equilibrium values into the Ka expression and solve for x, then convert to pH.

For the second part,
you know pH = pKa + log(base/acid)
(base) = (OH) that must be added
(acid) = 0.2-(OH)
I would plug that into the HH equation, solve for base and convert that to grams. I shall be happy to critique your work if you post it.

• Biochemistry -

Thanks Doc!

• Biochemistry -

Part A...
Solving for x we will get 4.028x10^-4
Plugging it in into pH equation, we will get pH of 3.39

Part B
5.76g

## Similar Questions

1. ### French

Could you please check this to make sure it's right. We are supposed to write in paragraph form what we would buy for a party, who we would invite, and where we would buy the food at. Could you please give me a grade on it (I'm in …
2. ### Chemistry

The triation of 50.00 mL of 0.025 00 M MES with 0.100 0 M NaOH. MES is a weak acid with pKa=6.27. Compute Ve, first. Show what happens at the four stages of the titration: Va = 0,2,5,10,10.1,11,12, and 12.2 mL. I NEED HELP!!!!
3. ### French

I should circle the most appropriate subject: 1) Maxime/elsa est née à paris 2) mon frere/ma sœur. S'est engagé dans la lutte contre le sida 3) mes parents/ mes cousines. Se sont installées en gualdeloupe 4) ils/elles sont partis …
4. ### French

5 - Les vacances You are preparing a family vacation in Europe. Rewrite each sentence using two pronouns. Pay particular attention to the agreement of the past participle. 1.-L'agence de voyages a envoyé les billets d'avion à mes …
5. ### French, foreign languages

Hi, I desperately need help with double object pronouns in French. Here are questions that I am working on and I can't make heads nor tails of them: L'agence de voyages a envoyé les billets d'avion à mes parents. Mes parents ont …
6. ### French, foreign languages

Hi, I desperately need help with double object pronouns in French. Here are questions that I am working on and I can't make heads nor tails of them: L'agence de voyages a envoyé les billets d'avion à mes parents. Mes parents ont …
7. ### biochemistry

You have 325 mL of an 0.11 M acetic acid solution. What volume (V) of 2.00 M NaOH solution must you add in order to prepare an acetate buffer of pH = 5.07?
8. ### Biochemistry

How would you make 100 mL of a carbonic acid buffer at 0.5 M and pH = 6.0 using 1.0 M NaHCO3 and either 1.0 M NaOH or 1.0 M HCl and water?
9. ### Biochemistry

Calculate the pH of a mixture of one mole of benzoic acid and two mole of sodium benzoate dissolved in 1 L of solution. The pKa of benzoic acid is 4.2. What is the final molar concentration of the buffer?
10. ### Biochemistry

Show Calculations used in mkaing 250mL of 0.5M sodium acetate ph 4.7. You are given: 1M acetic acid (weak acid) 1M sodium hydroxide (strong base) Sodium acetate buffer: ph 4.7 acetic acid pKa: 4.7 So far this is what I've gotten: pH …

More Similar Questions