What is the PH of an aqueous solution consisting of 0.070 M formic acid (HCOOH) and 0.070 M sodium formate (HCOONa)?

Answer 1

Use the Henderson-Hasselbalch equation.
pH = pKa + log (base)/(acid)
pH = ?
pKa = look up
(base) = 0.07
(acid) = 0.07

Answer 2

I am not really sure how the find the
pKa. Do I need to find the conjugate acid -base pair first?

Answer 3

pKa = -log Ka

Answer 4

I am not understand how to use log on my calculate, so no answer is calculating.

can you explain how to use log?

Answer 5

pKa = 7.6 for HCOOH
so pH= 7.6 + log [.07]/[.07}
pH = 7.6

is this correct or at least moving in the right direction?

Answer 6

Some is correct. I don't know how your calculator works (calculators aren't standard) but I can tell you how to proceed.
First, where did you get the pKa for formic acid? I looked it up on the web and found 3.77. You can get slightly different numbers depending upon where you look but that's fiarly close. The Ka is about 1.7E-4. So
pH = pKa + log (base)/(acid_
pH = 3.77 + log (0.07/0.07)
pH = 3.77 + log 1
and log 1 I thought everyone knew is zero and you really don't need a calculator for that.
Then pH = 3.77 + 0 = 3.77. Right?