What do I need to do?
2007-05-14 06:45:43 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Chemistry
Since benzoic acid is not a strong acid, you need to find the Ka value for it first, then work from there.
2007-05-14 06:51:55 · answer #1 · answered by hawkeye3772 4 · 0⤊ 0⤋
The Ka of benzoic acid is equal to 6.5E-5 (I looked it up. If this value is different from the one you have, then use whatever Ka value you have for benzoic acid.)
The Ka expression is (H+)(A-)/(HA) where HA = benzoic acid and A- = benzoate anion.
Let (H+) = (A-) = x
(HA) = 2.79
x^2 = (Ka)x(HA) = (6.5E-5)(2.79) = 1.8E-4 = x which is the concentration of the H+ ion.
Taking the negative log of 1.8E-4, you get the pH, which is 3.74.
2007-05-14 13:59:15 · answer #2 · answered by mrfarabaugh 6 · 0⤊ 0⤋
1. get its Ka
2. apply [H+] = root (Ka x molarity)
3. take the negative logarithm of [H+]
2007-05-14 13:51:06 · answer #3 · answered by Gervald F 7 · 0⤊ 0⤋