For the equation $\mathrm { CH } _ { 3 } \mathrm { CO } _ { 2 } ( \mathrm { aq } ) f \mathrm { H } ^ { + } ( \mathrm { aq } ) + \mathrm { CH } _ { 3 } \mathrm { CO } _ { 2 } ^ { - } ( \mathrm { aq } )$ , if the final concentrations of [H⁺], [CH₃CO₂^?], and [CH₃CO₂H] are 0.0014 M, 0.0036 M, and 1.00M respectively the value of K_a is _____.

Question

Quizplus · Accepted Answer

The given equation is a weak acid, weak base equilibrium equation, and can be written as: CH3CO2H(aq) + H2O(l) ⇌ CH3CO2-(aq) + H3O+(aq) Let the initial concentration of CH3CO2H be x. Then, the initial concentrations of CH3CO2-, H3O+ and H2O are all zero. At equilibrium, the concentration of CH3CO2- is also x (as one mole of CH3CO2H produces one mole of CH3CO2-). The concentration of H3O+ is given as 0.0014 M. The concentration of water can be assumed to be (55.6 - 0.0014) M, which is approximately 55.6 M. The equilibrium concentration of CH3CO2H can be calculated using the expression for Ka of the acid. Ka = [CH3CO2-][H3O+]/[CH3CO2H] Ka = x * 0.0014 / x = 0.0014 x = 0.0036 M Therefore, [CH3CO2H] = x = 0.0036 M [CH3CO2-] = x = 0.0036 M [H3O+] = 0.0014 M Substituting these values into the expression for K_a, we get: K_a = [CH₃CO₂H][H⁺]/[CH₃CO₂⁻] = (1.00 M)(0.0014 M) / (0.0036 M) = 0.389 M Taking the negative logarithm of this expression gives the pK_a value: pK_a = 5.409 Therefore, K_a = 5.0 ×10^-6.

For the Equation , If the Final Concentrations of [H+], [CH3CO2?], and [CH3CO2H]

For the Equation , If the Final Concentrations of [H⁺], [CH₃CO₂^?], and [CH₃CO₂H]