Nicotinic acid (niacin) is a monoprotic acid with the formula HC6H4NO2. A solution that is 0.012M in nicotinic acid has a pH of 3.39 at 25*C. What is the acid-ionization constant, Ka and pKa for this acid at 25*C?

Answer 1

Write the ionization equation.
Prepare an ICE chart.
You know pH and this will give you (H^+), (nicotine ion), and nicotinic acid concn. Plug these into the Ka expression and solve for Ka, then pKa. Post your work if you get stuck.