Asked by H
Activity Coefficient for Phosphate Buffers: How would I calculate the predicted pH for Na2HPO4 and NaH2PO4? For hypothetical pH 6- we added 94mL of H2PO4 and 6mL of HPO4 (for a total of 100mL). But how would I calculate "actual pH"?
We measured at two different strengths, 0.1M and 0.01M. For HPO4 the correction factor for 0.1M-0.45 and 0.01-0.75 and for H2PO4 0.1-0.74 and 0.01-0.93.
I know it's a similar equation to the HH equation with the added log(A coeff/HA coeff) but I'm unsure how to proceed from there.
We measured at two different strengths, 0.1M and 0.01M. For HPO4 the correction factor for 0.1M-0.45 and 0.01-0.75 and for H2PO4 0.1-0.74 and 0.01-0.93.
I know it's a similar equation to the HH equation with the added log(A coeff/HA coeff) but I'm unsure how to proceed from there.
Answers
Answered by
Heidi
How many moles of conjugate base (Na2HPO4) are present in 40mL of .010M buffer at pH 7.5 vs at pH 6?
Buffer was made up of Na2HPO4 and NaH2PO4.
pH=pKa +log[A/HA]; pKa=7.2.... When I did the calculations I got the same amount as if it were in a 0.1M buffer at the same pH's so I think I'm doing something wrong.
Buffer was made up of Na2HPO4 and NaH2PO4.
pH=pKa +log[A/HA]; pKa=7.2.... When I did the calculations I got the same amount as if it were in a 0.1M buffer at the same pH's so I think I'm doing something wrong.
Answered by
Heidi
Ignore the second post at 10:32, I'm going to post it as it's own question!
There are no AI answers yet. The ability to request AI answers is coming soon!
Submit Your Answer
We prioritize human answers over AI answers.
If you are human, and you can answer this question, please submit your answer.