Question

The concentration of $C_6{H}_6{O}_6^{2-}$ ion in the given solution of ascorbic acid is:

• A. $1\times {10}^{-12}$
• B. $8\times {10}^{-5}$
• C. $1\times {10}^{-8}$
• D. $1\times {10}^{-10}$

Answer 1

The correct option is A $1\times {10}^{-12}$

According to qestion

$C_6{H}_8{O}_6\rightleftharpoons C_6{H}_7{O}_6^{-}+H^{+}{K}_1=8\times {10}^{-5}$ ___(1)

$C_6{H}_7{O}_6^{-}\rightleftharpoons C_6{H}_6{O}_6^{2-}+H^{+}{K}_2=1\times {10}^{-12}$ __(2)

$HCl=1M$

$HCl\to \underset{1M}{H^{+}}+\underset{1M}{C{l}^{-}}$

From equation (2)

$K_2=\frac{\left[C_6{H}_6{O}_6^{2-}\right]\left[H^{+}\right]}{\left[C_6{H}_7{O}_6^{-}\right]}$

From equation (1) it is clear that $\left[H^{+}\right]=\left[C_6{H}_7{O}_6^{-}\right]$

therefore,

$K_2=\left[C_6{H}_6{O}_6^{2-}\right]$

Thus, concentration of $C_6{H}_6{O}_6^{2-}$ ion

$\left[C_6{H}_6{O}_6^{2-}\right]=K_2=1\times {10}^{-12}$

option - (A)