1. In general, **acid** + $\ce{H_2O} \rightleftharpoons$ **base** + $\ce{H_3O^+}$
2. It is called the Henderson-Hasselbach equation 
 $pH = pK_a + \log\frac{[base]}{[acid]}$
3. I believe the equilibrium constant for a such a neutralisation would look like $K_n = K_aK_b\frac{1}{K_w}$