You add 30ml of 1m of nh3 to a 50ml solution of 0,2 mgcl2. magnesium hydroxide (mg(oh)2) precipitates.
what is the minimum concentration of nh4+ that prevents the precipitation of mg(oh)2?
given information:
(mgoh2) ksp = 13
(nh3) kb = 10^-4.75
note: a complex formation between mg and nh4+ is ruled out.

Explanation:

The reaction equation will be as follows.

of = 13 and of =

Hence, concentration of =

                        =

                        = 4 M

As,

Hence,

                  13 =

              = 1.80276 M

Also, ionization constant of water is given as follows.

             ......... (1)

Now, put the value of in equation (1) as follows.

                             =

                             =

Also, =

Therefore, =

                              =

                              =

Since,

          ....... (2)

Hence, calculate the value of as follows.

              =

                              =

                              =

              =

Thus, we can conclude that the minimum concentration of that prevents the precipitation of is .

that's what i got you can count the number of atoms