20. What is the maximum concentration of Mg^2+ ion that remains dissolved in a solution that contains 0,7147 M NH_(3) and 0,2073MNH_(4)Cl (K_(sp) for Mg(OH)_(2) is 1,2times 10^-11;K_(b) for NH_(3) is 1,77times 10^-5 A. 1,9times 10^-7M B. 3,2times 10^-3M C. 1,3times 10^-3M D.. 6,4times 10^-6M

Question

Answer 1

To find the maximum concentration of

that remains dissolved, we need to consider the solubility product constant (

) for \( \text{Mg(OH)}_2 \) and the equilibrium expressions involving ammonia (

) and ammonium chloride (

).First, write the

expression for \( \text{Mg(OH)}_2 \):

Given:

Next, determine the concentration of hydroxide ions (

) from the given concentrations of

and

.The equilibrium expression for

in water is:

Using the base dissociation constant (

) for

:

Set up the expression for

:

Assume

is the concentration of

produced:

Since

is typically very small compared to the initial concentration of

, we can approximate:

Solve for

:

This

is the concentration of

.Now, use the

expression for \( \text{Mg(OH)}_2 \):

Solve for

:

Therefore, the maximum concentration of

that remains dissolved is approximately

M, which is closest to option A.**Answer: A.

M **

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