Question

Consider an aqueous solution, 0.1 M each in $HOCN,HCOOH,(COOH{)}_2$ and $H_3{PO}_4$, for $HOCN$, we can write $K_a\left(HOCN\right)=\frac{\left[H^{+}\right]\left[{OCN}^{-}\right]}{\left[HOCN\right]}.\left[H^{+}\right]$ in this expression refers to:

• A. $H^{+}$ ions released by $HOCN$
• B. sum of $H^{+}$ ions released by all monoprotic acids
• C. sum of $H^{+}$ ions released only the first dissociation of all the acids.
• D. overall $H^{+}$ ion concentration in the solution.

Answer 1

Answer: (A)

$H^{+}$ ions released by $HOCN$

$\left(A\right)H^{+}$ ions released by $HOCN$ as follows:

$HOCN\to H^{+}+OC{N}^{-}$

$K_a\left(HOCN\right)=\frac{\left[H^{+}\right]\left[{OCN}^{-}\right]}{\left[HOCN\right]}$

Option A is correct.