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 .

a). in this case, dh> 0 and sd> 0. if t becomes larger, the term "-tds" will become more negative. at some point, it is possible that -dts will be more negative than the dh is positive, and the reaction will become spontaneous. this is probably the correct answer, but you should look at all of the other possibilities and make sure of that.

hypostyle hall;