Question

A student has a solution of 0.05 ammonium chloride. The K_a for ammonium is 5.7x10^-10. Using the systematic approach, solve for the concentrations of H₃0⁺, NH₃, and NH₄⁺. (Analytical Chemistry)

Answer 1

concentration of NH4Cl = 0.05 M

Ka = 5.7 x 10^-10

NH4+   + H2O    ------------>   NH3 + H3O+

0.05                                          0           0

0.05 - x                                     x           x

Ka = x^2 / 0.05 - x

5.7 x 10^-10 = x^2 / 0.05 - x

x = 5.34 x 10^-6

[H3O+] = 5.34 x 10^-6 M

[NH3] = 5.34 x 10^-6 M

[NH4+] = 0.05 M