Posted by student on Sunday, February 3, 2008 at 2:49pm.
I have already posted this and never got a response, please help.
here is my data from lab:
Buffer1: HPO4- weight 3.412g; original pH
Buffer 2: HEPES wt: 1.090g original pH 10.08
pH of 0.1M: 7.5;
pH of 0.01: 7.72;
pH of 0.001M: 7.87
PH of 0.1M: 7.5
ph of 0.01 M: 7.42
pH of 0.001M: 7.42
The problem will be done for one of the buffers made.
A) What is the ratio of A-/HA in your buffer after you adjusted its pH to the required value? (pH goal: 7.5)
B) How many micromoles of A- and HA are present in the solution?
C) If you now add 3 mL of 1 M NaOH, will you still have a valid buffer?
If necessary, here are the pka values and molecular weights: HEPES: pka 7.55; mw= 238.3; phosphate (HPO4-) pka1: 2.12 pka2: 7.21; pka 3: 12.32; mw=142.0
HERE ARE HINTS I HAVE BEEN GIVEN:
A. Use the Henderson Hasselbach equation.
B. micromole = 0.001 mole
you know that the HA + A- have to equal number of moles in the 0.1 M solution
C. Will all of the HA form to the A- form be converted? Or will some of it remain?
Thank you very much!!!
Answer this Question
chemistry lab - Could someone help me with this? i am tired of it. here is my ...
chemistry - The pKa of HEPES is 7.55 at 20 degrees C, and its MW is 238.31. ...
science(chem) - The pKa of HEPES is 7.55 at 20C and it's MW is 238.31. Calculate...
Biochem - HEPES, is a commonly used component of physiological buffers. The PKa ...
Biochemistry - Sorry! HEPES, is a commonly used component of physiological ...
Chemistry - If you start with 200 ml of 0.1M HEPES buffer (pH 7.5) and add 1.25 ...
Biochemistry DR.BOB - How many grams of NaOH(Mr 40) must be added to 100 ml of ...
chem - I posted a question earlier that I was having trouble with, but I was ...
science - chemistry pH problems - Here is the hint I received on how to solve ...
Biochem - We will need 0.5L extraction buffer with 25 mM HEPES, 1 mM EDTA, and 1...