Calculate the pH of a solution of ammonium acetate (CH3COONH4) 0,85M knowing that for NH3 Kb = 1,79x10-5 and CH3COOH Ka = 1,76x10-5 and commented on the result obtained. Then calculate the percentage of acetic acid product at equilibrium
(H^+) = sqrt(Kw/KaKb) and convert H^+ to pH.
ammonium acetate = NH4Ac
NH4Ac + HOH ==> NH4OH + HAc
Plug in H^+ to Ka expression for HAc and calculate HAc.
To calculate the pH of the solution of ammonium acetate, we need to consider the dissociation of ammonium acetate into its constituent ions.
Ammonium acetate (CH3COONH4) dissociates in water to form acetate ions (CH3COO-) and ammonium ions (NH4+). The ammonium ion is weakly acidic, while the acetate ion is the conjugate base of a weak acid.
We can set up an equilibrium expression for the dissociation of ammonium acetate as follows:
CH3COONH4 ⇌ CH3COO- + NH4+
The concentration of ammonium acetate (CH3COONH4) is given as 0.85 M. At equilibrium, some of the ammonium acetate will dissociate into its ions, so let's assume that x M of ammonium acetate dissociates. The equilibrium concentration of acetate ion (CH3COO-) and ammonium ion (NH4+) will both be x M.
Using the given values of the dissociation constants:
Kb for NH3 = 1.79×10^-5
Ka for CH3COOH = 1.76×10^-5
We can set up an equation for the equilibrium using the Kb value:
Kb = [NH4+][OH-] / [NH3]
Since the concentration of hydroxide ion (OH-) is negligible compared to the ammonium ion concentration, we can assume it to be zero. Therefore, the equation simplifies to:
Kb = [NH4+]/[NH3]
Using the equilibrium concentration values, we have:
1.79×10^-5 = x / (0.85 - x)
Solving this equation will give us the value of x. Once we have x, we can calculate the concentrations of NH4+ and NH3 at equilibrium.
Next, we need to calculate the pOH and pH of the solution:
pOH = -log[OH-]
pH = 14 - pOH
Finally, we can calculate the percentage of acetic acid product at equilibrium. Since acetic acid (CH3COOH) is a weak acid, it will not completely dissociate. The percentage of acetic acid product at equilibrium can be calculated using the equation:
(Concentration of dissociated acetic acid / Initial concentration of acetic acid) x 100%
With the given data and calculations, we can obtain the pH of the solution and the percentage of acetic acid product at equilibrium.