Final answer:
To determine the percentage of butanoic acid that is dissociated in a 1.2mM aqueous solution, we can use the concept of percent ionization. By setting up the equilibrium expression for the dissociation of butanoic acid and using the given concentration, we can calculate the concentration of the dissociated ions and then determine the percentage of dissociation.
Step-by-step explanation:
The percentage of butanoic acid that is dissociated in a 1.2mM aqueous solution can be determined using the concept of percent ionization. Butanoic acid is a weak acid and only a small fraction of it will dissociate into ions. Using the given concentration, we can calculate the concentration of the dissociated ions and then determine the percentage of dissociation.
First, let's calculate the concentration of the dissociated ions. Since butanoic acid is a weak acid, we can assume that only a small fraction is dissociated. Let's say that x is the concentration of the dissociated ions. Then, the concentration of butanoic acid in the solution is 1.2mM - x.
Next, we can set up the equilibrium expression for the dissociation of butanoic acid: C3H7CO2H (aq) + H2O (l) → C3H7CO2- (aq) + H3O+ (aq). The equilibrium constant for this reaction is the Ka value for butanoic acid, which can be found in a reference table.
Finally, to determine the percentage of dissociation, we divide the concentration of the dissociated ions (x) by the initial concentration of the butanoic acid (1.2mM) and multiply by 100. This will give us the percentage of butanoic acid that is dissociated in the solution.