Question

A student prepares a 0.61mM aqueous solution of propionic acid C2H5CO2H. Calculate the fraction of propionic acid that is in the dissociated form in his solution. Express your answer as a percentage. You will probably find some useful data in the ALEKS Data resource.

Answer 1

Answer:

The 13.76% of propionic acid is in the dissociated form in the solution

Explanation:

Concentration of propionic acid = c = 0.61mM = $0.61\times 10^{-3}M$

$mM=10^{-3}M$

Degree of dissociation = α

$C2H5CO2H\rightleftharpoons C2H5COO^-+H^+$

At initial

c                             0   0

At equilibrium

c - cα                     cα   cα

The value of dissociation constant of propionic acid = $K_a=1.34\times 10^{-5}$

The expression of dissociation constant of propionic acid is given by :

$K_a=\frac{c\times alpha c\times \alpha}{c(1-\alpha )}$

$K_a=\frac{c\alpha ^2}{(1-\alpha )}$

$1.34\times 10^{-5}=\frac{0.61\times 10^{-3}M\times \alpha ^2}{(1-\alpha )}$

Solving the equation for $\alpha$:

$\alpha =0.1376$

$\alpha=\frac{0.1376}{1}\times 100=13.76\%$

The 13.76% of propionic acid is in the dissociated form in the solution