Answer to Question #8622 in Organic Chemistry for Imani

Question

a solution is created by dissolving 1.935g of sodium acetate, NaCH3CO2,in 850.0mL of .405M acetic acid,CH3COOH,at 25'C.Ka for acetic acid is 1.8*10^-5 at 25'C. assume that the volume of the solution does not change. find the concertratioof ion,CH3COO- in the final solution

Answer 1

CH₃COOH <-> H⁺ + CH₃COO^-

K_a = [H⁺][CH₃COO-]/[CH₃COOH]

CH₃COONa <-> CH₃COO^- + Na⁺

Sodium acetate is a strong electrolyte and breaks up into ions completely

1.935 n
CH₃COONa <-> CH₃COO^- + Na⁺
82

n = 0.0236 mol
C = 0.0236/0.85 = 0.0278 M (mol/L)

using that K_a of final solution is:

K_a = [H⁺][0.0278 + x]/0.405 = 1.8*10^-5
[H⁺] = x too because CH₃COOH <-> H⁺ + CH₃COO^-

x*(0.0278+x) = 1.8*10^-5 * 0.405
x^2 + 0.0278x - 7,29*10^-6 = 0
x = 2.59*10^-4 M
final C of CH₃COO^- = 0.0278 + 0.000259 = 0.02806 M