Question

In the system, $Ca{F}_2\left(s\right)\rightleftharpoons C{a}^{2+}(aq.)+2F^{-}(aq.)$, increasing the concentration of $C{a}^{2+}$ ions $4$ times will cause the equilibrium concentration of $F^{-}$ ions to change to:

• A. $1/4$ of the initial value
• B. $1/2$ of the initial value
• C. $2$ times of the initial value
• D. none of the above

Answer 1

The correct option is B $1/2$ of the initial value

$K_c=\left[C{a}^{2+}\right]{\left[F^{-}\right]}^2$

We have, $\left[C{a}^{2+}\right]=4\times \left[C{a}^{2+}\right]$

Therefore,

For $K_c$ constant $\left[F^{-}\right]shouldbe\frac{\left[F^{-}\right]}{2}$