Question

What is the pH of 1.05 M Cu(NO3)2 ? Ka=3 x 10^-8 Ka is a acid.

Answer 1

Cu2+ (aq) + 6 H2O (l)    ------------> [Cu(H2O)6]2+ (aq)

[Cu(H2O)6]2+ (aq) +   H2O (l)   ------------->   [Cu(H2O)5. OH]+ (aq) + H3O+ (aq)

   1.05                                                                         0                              0

1.05 - x                                                                     x                               x

Ka = x^2 / 1.05 - x

3.0 x 10^-8 = x^2 / 1.05 - x

x = 1.775 x 10^-4

[H3O+] = 1.775 x 10^-4 M

pH = -log (H3O+)

     = - log (1.775 x 10^-4 )

pH = 3.75