Formic acid, HCOOH, has Ka = 1.8 × 10⁻⁴…

Salt hydrolysis: an ion from a weak acid or a weak base reacts with water. A salt of a weak acid and a strong base gives a basic solution, $\text{pH} = 7 + \tfrac{1}{2}(\text{p}K_a + \log C)$. A salt of a strong acid and a weak base gives an acidic one, $\text{pH} = 7 - \tfrac{1}{2}(\text{p}K_b + \log C)$. $K_h = K_w/K_a$ and $h = \sqrt{K_h/C}$, with $K_w = 1.0 \times 10^{-14}$ at $298\ \text{K}$.