Question

Calculate the solubility of zn(oh)2(s) in 2.0 m naoh solution. (hint: you must take into account the formation of zn(oh)2−4, which has a kf=2×1015.)

Answer 1

when we have:

Zn(OH)2 → Zn2+ 2OH-  with Ksp = 3 x 10 ^-16

and:

Zn2+ + 4OH- → Zn(OH)4 2-  with Kf = 2 x 10^15
 
by mixing those equations together:

Zn(OH)2 + 2OH- → Zn(OH)4 2- with K = Kf *Ksp = 3 x 10^-16 * 2x10^15 =0.6

by using ICE table:

         Zn(OH)2 + 2OH- → Zn(OH)4 2-

initial                     2m              0

change                  -2X                +X     

Equ                       2-2X                 X

when we assume that the solubility is X

and when K = [Zn(OH)4 2-] / [OH-]^2

        0.6 = X / (2-2X)^2    by solving this equation for X

∴ X = 0.53 m

∴ the solubility of Zn(OH)2 = 0.53 M

Answer 2

The solubility of Zn(OH)₂(s) in 2.0 M Sodium hydroxide solution is 1.25 × 10⁻¹⁶ M.

How do we calculate the solubility?

Solubility of any compound can be calculated by using the formula of solubility product constant (Ksp), which is equal to the product of the solubility concentration of their respective ions.

Given that value of Kf for Zn(OH)₂ = 2 × 10¹⁵

We know that, Kf × Ksp = 1

Ksp of Zn(OH)₂ = 1 /  2 × 10¹⁵ = 5 × 10⁻¹⁶

For Zn(OH)₂ Ksp will be calculated as:

Ksp = [Zn²⁺][OH⁻]²

If the solubility be x,

Then the value of [OH⁻] in Zn(OH)₂ =2s

And value of [OH⁻] in 2M NaOH = 2 M

On putting all these values on the Ksp equation, we get

Ksp = [s][2s+2]²

Ksp = 4s (as value of 2s is very less as compare to 2, so it will be negligible)

s = Ksp / 4

s = 5×10⁻¹⁶ / 4

s = 1.25 × 10⁻¹⁶ M

Hence required value of solubility is 1.25 × 10⁻¹⁶ M.

To know more about Ksp, visit the below link:
https://brainly.com/question/25134328