Question

Ionization constant $\left(K_a\right)$ for three weak monobasic acids $HA$, $HB$ and $HD$ are ${10}^{-3},{10}^{-7}$ and ${10}^{-9}$ ,respectively at ${25}^{o}C$. Which of the following is correct prediction?

• A. ${\left(pH\right)}_{NaA}>({pH)}_{NaB}$
• B. ${\left(pH\right)}_{NaA}<({pH)}_{NaB}$
• C. ${\left(pH\right)}_{NaA}>({pH)}_{NaD}$
• D. ${\left(pH\right)}_{NaB}=7$

Answer 1

The correct option is B ${\left(pH\right)}_{NaA}<({pH)}_{NaB}$

$pH=p{K}_a+{\log }_{10}\left(\frac{\left[salt\right]}{\left[Acid\right]}\right)$ {Henderson Hassel batch equation}

$\therefore {\left(pH\right)}_{NaA}<{\left(pH\right)}_{NaB}$