# is pKa the same as pH?

Discussion in 'DAT Discussions' started by drzakisadiq, Jul 28, 2008.

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1. ### drzakisadiq 2+ Year Member

107
0
Jun 30, 2008
just wondering, a bit confused on terminology here.

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3. ### Albuterol 7+ Year Member

Dec 14, 2007
North Jersey
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

4. ### drzakisadiq 2+ Year Member

107
0
Jun 30, 2008
thanks, so if in a problem i were given the pKa, how would i convert that to pH?

5. ### PreDent2009 5+ Year Member

220
0
Dec 20, 2007
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.

6. ### Albuterol 7+ Year Member

Dec 14, 2007
North Jersey
u can use the henderson-hasselbach equation
pH= pKa + log [conj base]/[wa]

im not sure of others but hopefully someone else knows.

7. ### doc3232 7+ Year Member

Feb 15, 2008
You can compare the two, but they are not the same.
They are equal only if [HA] = [A-]