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 07-28-2008, 07:46 PM #1 Senior Member   Status: Pre-Dental Join Date: Jun 2008 Posts: 107 is pKa the same as pH? SDN Members don't see this ad. (About Ads) just wondering, a bit confused on terminology here.
 07-28-2008, 07:49 PM #2 1K Member     Status: Dental Student Join Date: Dec 2007 Location: North Jersey Posts: 1,188 pKa = -log of [Ka] pH = -log of [H+] Ka is the acid dissociation constant = [H+][A-]/[HA] pH= pKa when the conjugate base = weak acid at the half-way point on a titration curve the lower the pKa the more acidic the solution is the lower the pH the more acidic the solution is
 07-28-2008, 07:51 PM #3 Senior Member   Status: Pre-Dental Join Date: Jun 2008 Posts: 107 thanks, so if in a problem i were given the pKa, how would i convert that to pH?
07-28-2008, 07:54 PM   #4
Senior Member

Join Date: Dec 2007
Posts: 219

They would also have to give you the concentration of the acid and its conjugate base so you could use the henderson hasselbach formula. Otherwise, it would be pretty impossible to derive the pKa. You can however tell whether the acid is strong or weak, etc.

Quote:
 Originally Posted by drzakisadiq thanks, so if in a problem i were given the pKa, how would i convert that to pH?

 07-28-2008, 08:00 PM #5 1K Member     Status: Dental Student Join Date: Dec 2007 Location: North Jersey Posts: 1,188 u can use the henderson-hasselbach equation pH= pKa + log [conj base]/[wa] im not sure of others but hopefully someone else knows.
 07-28-2008, 08:00 PM #6 3K Member     Status: Dental Student Join Date: Feb 2008 Posts: 3,811 You can compare the two, but they are not the same. They are equal only if [HA] = [A-]

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