Question

Hydrocyanic acid has a Ka of 4.0

Answer 1

Answer:

0.002 %

Explanation:

Given that:

$K_{a}=4.0\times 10^{-10}$

Concentration = 1.0 M

Consider the ICE take for the dissociation of Hydrocyanic acid as:

                                      HCN    ⇄     H⁺ +        CN⁻

At t=0                            1.0                -              -

At t =equilibrium        (1.0-x)                x           x            

The expression for dissociation constant of Hydrocyanic acid is:

$K_{a}=\frac {\left [ H^{+} \right ]\left [ {CN}^- \right ]}{[HCN]}$

$4.0\times 10^{-10}=\frac {x^2}{1.0-x}$

x is very small, so (1.0 - x) ≅ 1.0

Solving for x, we get:

x = 2×10⁻⁵  M

Percentage ionization = $\frac {2\times 10^{-5}}{1.0}\times 100=0.002 \%$