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

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

Step-by-step explanation:

Concentration of propionic acid = c = 0.61mM =
`0.61* 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* 10^(-5)`

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

`K_a=(c* alpha c* \alpha)/(c(1-\alpha ))`

`K_a=(c\alpha ^2)/((1-\alpha ))`

`1.34* 10^(-5)=(0.61* 10^(-3)M* \alpha ^2)/((1-\alpha ))`

Solving the equation for
`\alpha`:

`\alpha =0.1376`

`\alpha=(0.1376)/(1)* 100=13.76\%`

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