[GymClassHero001]

I really could use some help trying to figure out an unknown Ka for a lab. 1) test tube has 5.00 mL of 2.00 M unknown acid/ 2.50 mL of 1.00 M NaOH/ and 7.50 mL of H₂0 to make 15 mL total. The pH is 3.96.
How do I find Ka? What are the steps? I can do the calculations. I'm sure that 10^-3.96 = 1.09x10^-4 will come into the equation somewhere?

[Borek]

pH can be expressed as a function of pKa and concentrations of acid and conjugate base - Henderson-Hasselbalch equation.