Acids and Bases Questions

Phosphoric acid ionizes in three steps with their ionization constant values $K_{a1}$, $K_{a2}$ and $K_{a3}$, respectively, while $K$ is the overall ionization constant. Which of the following statements are true?A. $\log K=\log K_{a1}+\log K_{a2}+\log K_{a3}$ B. ${\text{H}}_3{\text{PO}}_4$ is a stronger acid than ${\text{H}}_2{\text{PO}}_4^{-}$ and ${\text{HPO}}_4^{2-}$ C. $K_{a1}>K_{a2}>K_{a3}$ D. $K_{a1}=\frac{K_{a3}+K_{a2}}{2}$ Choose the correct answer from the options given below:

Which of the following is least likely to behave as a Lewis base?

The dissociation constants for acetic acid and $\text{HCN}$ at $25^{\circ }\text{C}$ are $1.5\times 10^{-5}$ and $4.5\times 10^{-10}$ respectively. The equilibrium constant for the equilibrium ${\text{CN}}^{-}+{\text{CH}}_3\text{COOH}\rightleftharpoons \text{HCN}+{\text{CH}}_3{\text{COO}}^{-}$ would be: